{"id":18117,"date":"2026-07-14T16:29:20","date_gmt":"2026-07-14T16:29:20","guid":{"rendered":"https:\/\/withcode.tech\/media\/?p=18117"},"modified":"2026-07-19T15:12:47","modified_gmt":"2026-07-19T15:12:47","slug":"css-pseudo-elements","status":"publish","type":"post","link":"https:\/\/withcode.tech\/media\/css-pseudo-elements\/","title":{"rendered":"\u30102026\u5e74\u7248\u3011CSS\u7591\u4f3c\u8981\u7d20 ::before\/::after\u306e\u4f7f\u3044\u65b9\uff5ccontent\u3067\u88c5\u98fe\u3092\u30b3\u30d4\u30da\u5b9f\u88c5"},"content":{"rendered":"<p class=\"wp-block-paragraph\">CSS\u306e <code>::before<\/code> \u3068 <code>::after<\/code> \u306f\u3001HTML\u3092\u4e00\u5207\u5909\u3048\u305a\u306b\u8981\u7d20\u306e\u524d\u5f8c\u306b\u88c5\u98fe\u3092\u5dee\u3057\u8fbc\u3081\u308b\u7591\u4f3c\u8981\u7d20\u3067\u3059\u3002\u898b\u51fa\u3057\u306e\u30c7\u30b3\u30ec\u30fc\u30b7\u30e7\u30f3\u3001\u4e0b\u7dda\u30a8\u30d5\u30a7\u30af\u30c8\u3001\u5439\u304d\u51fa\u3057\u306e\u4e09\u89d2\u3001\u30a2\u30a4\u30b3\u30f3\u98a8\u306e\u8a18\u53f7\u306a\u3069\u3001\u30c7\u30b6\u30a4\u30f3\u306e\u5e45\u3092\u5927\u304d\u304f\u5e83\u3052\u308b\u6a5f\u80fd\u3068\u3057\u3066\u3001\u73fe\u5834\u306eCSS\u3067\u6bce\u65e5\u4f7f\u308f\u308c\u3066\u3044\u307e\u3059\u3002<\/p>\n\n\n<p class=\"wp-block-paragraph\">\u300ccontent\u30d7\u30ed\u30d1\u30c6\u30a3\u304c\u5fc5\u8981\u306a\u306e\u306f\u308f\u304b\u308b\u3051\u3069\u3001\u3069\u3053\u306b\u4f55\u3092\u66f8\u3051\u3070\u3044\u3044\u306e\uff1f\u300d\u300cposition\u3092\u4f7f\u3046\u5834\u9762\u304c\u3044\u3064\u3082\u3088\u304f\u308f\u304b\u3089\u306a\u3044\u300d\u300c\u601d\u3044\u901a\u308a\u306b\u8868\u793a\u3055\u308c\u306a\u3044\u539f\u56e0\u304c\u63b4\u3081\u306a\u3044\u300d\u3068\u3044\u3046\u58f0\u3092\u3088\u304f\u805e\u304d\u307e\u3059\u3002\u3053\u306e\u8a18\u4e8b\u3067\u306f\u57fa\u672c\u306e\u66f8\u304d\u65b9\u304b\u3089\u5b9f\u52d9\u3067\u4f7f\u3048\u308b\u30b3\u30d4\u30da\u30b5\u30f3\u30d7\u30eb\u307e\u3067\u3001\u9806\u3092\u8ffd\u3063\u3066\u4e01\u5be7\u306b\u89e3\u8aac\u3057\u307e\u3059\u3002<\/p>\n\n\n<p class=\"wp-block-paragraph\">\u5b8c\u5168\u306aHTML\uff0bCSS\u306e\u30b5\u30f3\u30d7\u30eb\u3092\u8907\u6570\u63b2\u8f09\u3057\u3066\u3044\u308b\u306e\u3067\u3001\u30d6\u30e9\u30a6\u30b6\u3067\u78ba\u8a8d\u3057\u306a\u304c\u3089\u8aad\u307f\u9032\u3081\u3066\u304f\u3060\u3055\u3044\u3002\u8aad\u307f\u7d42\u308f\u308b\u9803\u306b\u306f\u3001\u7591\u4f3c\u8981\u7d20\u3092\u81ea\u5728\u306b\u4f7f\u3044\u3053\u306a\u305b\u308b\u3088\u3046\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n\n\n<p class=\"wp-block-paragraph\">\u5148\u306b\u3001\u3053\u306e\u8a18\u4e8b\u306e\u7d50\u8ad6\u3092\u307e\u3068\u3081\u307e\u3059\u3002<\/p>\n\n<ul class=\"wp-block-list\">\n<li><code>::before<\/code> \/ <code>::after<\/code> \u306f <code>content<\/code> \u30d7\u30ed\u30d1\u30c6\u30a3\u304c\u5fc5\u9808\u3002\u3053\u308c\u304c\u306a\u3044\u3068\u4f55\u3082\u8868\u793a\u3055\u308c\u306a\u3044<\/li>\n<li>\u88c5\u98fe\u3092\u300c\u6d6e\u304b\u305b\u3066\u300d\u914d\u7f6e\u3057\u305f\u3044\u3068\u304d\u306f <code>position: absolute<\/code> \u3068\u89aa\u8981\u7d20\u306b <code>position: relative<\/code> \u3092\u30bb\u30c3\u30c8\u3067\u4f7f\u3046<\/li>\n<li><code>content: \"\"<\/code>\uff08\u7a7a\u6587\u5b57\uff09\u306b\u3059\u308c\u3070\u7d14\u7c8b\u306a\u88c5\u98fe\u30dc\u30c3\u30af\u30b9\u3068\u3057\u3066\u4f7f\u3048\u308b<\/li>\n<li>\u5358\u4e00\u30b3\u30ed\u30f3\uff08<code>:before<\/code>\uff09\u3068\u4e8c\u91cd\u30b3\u30ed\u30f3\uff08<code>::before<\/code>\uff09\u306e\u52d5\u4f5c\u306f\u540c\u3058\u3060\u304c\u3001CSS3\u4ee5\u964d\u306f\u4e8c\u91cd\u30b3\u30ed\u30f3\u304c\u6b63\u5f0f\u8868\u8a18<\/li>\n<\/ul>\n\n\n<h2 class=\"wp-block-heading\">::before \u3068 ::after \u306e\u57fa\u672c\u69cb\u6587<\/h2>\n\n<p class=\"wp-block-paragraph\">\u7591\u4f3c\u8981\u7d20\u306f\u300c\u30bb\u30ec\u30af\u30bf\u30fc::\u7591\u4f3c\u8981\u7d20\u540d { \u30d7\u30ed\u30d1\u30c6\u30a3: \u5024; }\u300d\u306e\u5f62\u3067\u66f8\u304d\u307e\u3059\u3002<code>::before<\/code> \u306f\u9078\u629e\u3057\u305f\u8981\u7d20\u306e\u5185\u5bb9\u306e\u76f4\u524d\u3001<code>::after<\/code> \u306f\u76f4\u5f8c\u306b\u4eee\u60f3\u7684\u306a\u8981\u7d20\u3092\u751f\u6210\u3057\u307e\u3059\u3002\u5b9f\u969b\u306eDOM\u306b\u306f\u8ffd\u52a0\u3055\u308c\u305a\u3001CSS\u3060\u3051\u3067\u5236\u5fa1\u3067\u304d\u308b\u306e\u304c\u5927\u304d\u306a\u7279\u5fb4\u3067\u3059\u3002<\/p>\n\n<p class=\"wp-block-paragraph\">\u6700\u4f4e\u9650\u5fc5\u8981\u306a\u30d7\u30ed\u30d1\u30c6\u30a3\u306f <code>content<\/code> \u3060\u3051\u3067\u3059\u3002\u3053\u308c\u3092\u66f8\u304d\u5fd8\u308c\u308b\u3068\u7591\u4f3c\u8981\u7d20\u306f\u751f\u6210\u3055\u308c\u307e\u305b\u3093\u3002<\/p>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>\/* ::before \u306e\u57fa\u672c *\/\n.element::before {\n  content: \"\u3053\u3053\u304c before\";\n}\n\n\/* ::after \u306e\u57fa\u672c *\/\n.element::after {\n  content: \"\u3053\u3053\u304c after\";\n}\n\n\/* display\u306e\u30c7\u30d5\u30a9\u30eb\u30c8\u306finline *\/\n\/* \u30dc\u30c3\u30af\u30b9\u30e2\u30c7\u30eb\u3092\u4f7f\u3046\u306a\u3089display: block\u304binline-block\u3092\u6307\u5b9a *\/\n.element::before {\n  content: \"\";\n  display: block;\n  width: 40px;\n  height: 4px;\n  background: #d16176;\n}<\/code><\/pre><\/div>\n\n\n<p class=\"wp-block-paragraph\">\u5b9f\u969b\u306eHTML\u306b\u5f53\u3066\u306f\u3081\u3066\u78ba\u8a8d\u3057\u3066\u307f\u307e\u3057\u3087\u3046\u3002<\/p>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-markup\" data-lang=\"HTML\"><code>&lt;!DOCTYPE html&gt;\n&lt;html lang=\"ja\"&gt;\n&lt;head&gt;\n&lt;meta charset=\"UTF-8\"&gt;\n&lt;meta name=\"viewport\" content=\"width=device-width, initial-scale=1.0\"&gt;\n&lt;title&gt;\u7591\u4f3c\u8981\u7d20\u306e\u57fa\u672c&lt;\/title&gt;\n&lt;style&gt;\n.label::before {\n  content: \"\u3010\";\n  color: #d16176;\n  font-weight: bold;\n}\n.label::after {\n  content: \"\u3011\";\n  color: #d16176;\n  font-weight: bold;\n}\n&lt;\/style&gt;\n&lt;\/head&gt;\n&lt;body&gt;\n&lt;p class=\"label\"&gt;\u91cd\u8981\u306a\u304a\u77e5\u3089\u305b&lt;\/p&gt;\n&lt;\/body&gt;\n&lt;\/html&gt;<\/code><\/pre><\/div>\n\n\n<p class=\"wp-block-paragraph\">\u8868\u793a\u7d50\u679c\u306f\u300c\u3010\u91cd\u8981\u306a\u304a\u77e5\u3089\u305b\u3011\u300d\u306b\u306a\u308a\u307e\u3059\u3002HTML\u306e\u30c6\u30ad\u30b9\u30c8\u306f\u300c\u91cd\u8981\u306a\u304a\u77e5\u3089\u305b\u300d\u3060\u3051\u3067\u3059\u304c\u3001CSS\u304c\u524d\u5f8c\u306b\u62ec\u5f27\u3092\u8ffd\u52a0\u3057\u3066\u3044\u307e\u3059\u3002\u3053\u308c\u304c\u7591\u4f3c\u8981\u7d20\u306e\u57fa\u672c\u7684\u306a\u50cd\u304d\u3067\u3059\u3002<\/p>\n\n\n<h2 class=\"wp-block-heading\">content \u30d7\u30ed\u30d1\u30c6\u30a3\u306b\u6307\u5b9a\u3067\u304d\u308b\u5024<\/h2>\n\n<p class=\"wp-block-paragraph\"><code>content<\/code> \u306b\u306f\u6587\u5b57\u5217\u30fb\u7a7a\u6587\u5b57\u30fbattr()\u306a\u3069\u8907\u6570\u306e\u7a2e\u985e\u306e\u5024\u3092\u6307\u5b9a\u3067\u304d\u307e\u3059\u3002\u305d\u308c\u305e\u308c\u306e\u7528\u9014\u3092\u6574\u7406\u3057\u307e\u3057\u3087\u3046\u3002<\/p>\n\n\n<h3 class=\"wp-block-heading\">\u6587\u5b57\u5217\u30fb\u8a18\u53f7\u3092\u5165\u308c\u308b<\/h3>\n\n<p class=\"wp-block-paragraph\">\u30b7\u30f3\u30b0\u30eb\u30af\u30a9\u30fc\u30c8\u307e\u305f\u306f\u30c0\u30d6\u30eb\u30af\u30a9\u30fc\u30c8\u3067\u56f2\u3093\u3060\u6587\u5b57\u5217\u3092\u305d\u306e\u307e\u307e\u8868\u793a\u3057\u307e\u3059\u3002\u7d75\u6587\u5b57\u3084\u7279\u6b8a\u8a18\u53f7\u3082\u4f7f\u3048\u307e\u3059\u3002<\/p>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>\/* \u6587\u5b57\u5217 *\/\n.note::before {\n  content: \"\u203b \";\n}\n\n\/* \u8a18\u53f7 *\/\n.arrow::after {\n  content: \" \u2192\";\n}\n\n\/* \u7d75\u6587\u5b57 *\/\n.check::before {\n  content: \"\u2714 \";\n  color: #4CAF50;\n}\n\n\/* Unicode\u30a8\u30b9\u30b1\u30fc\u30d7\uff08\u30c1\u30a7\u30c3\u30af\u30de\u30fc\u30af\uff09 *\/\n.check2::before {\n  content: \"\u00b93  \";\n  color: #4CAF50;\n}<\/code><\/pre><\/div>\n\n\n<h3 class=\"wp-block-heading\">\u7a7a\u6587\u5b57\uff08\u88c5\u98fe\u30dc\u30c3\u30af\u30b9\u3068\u3057\u3066\u4f7f\u3046\uff09<\/h3>\n\n<p class=\"wp-block-paragraph\"><code>content: \"\"<\/code> \u306b\u3059\u308b\u3068\u3001\u30c6\u30ad\u30b9\u30c8\u306a\u3057\u306e\u7d14\u7c8b\u306a\u30dc\u30c3\u30af\u30b9\u3092\u751f\u6210\u3067\u304d\u307e\u3059\u3002\u4e0b\u7dda\u30fb\u30aa\u30fc\u30d0\u30fc\u30ec\u30a4\u30fb\u4e09\u89d2\u306a\u3069\u3001\u5f62\u72b6\u3092\u4f5c\u308b\u88c5\u98fe\u3067\u3088\u304f\u4f7f\u3044\u307e\u3059\u3002<\/p>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>\/* \u4e0b\u7dda\u88c5\u98fe *\/\n.underline-deco {\n  position: relative;\n  display: inline-block;\n}\n.underline-deco::after {\n  content: \"\";\n  position: absolute;\n  bottom: -4px;\n  left: 0;\n  width: 100%;\n  height: 3px;\n  background: #d16176;\n  border-radius: 2px;\n}<\/code><\/pre><\/div>\n\n\n<h3 class=\"wp-block-heading\">attr() \u3067 HTML \u5c5e\u6027\u5024\u3092\u8868\u793a\u3059\u308b<\/h3>\n\n<p class=\"wp-block-paragraph\"><code>attr(\u5c5e\u6027\u540d)<\/code> \u3092\u4f7f\u3046\u3068\u3001HTML\u8981\u7d20\u306e\u5c5e\u6027\u5024\u3092content\u5185\u3067\u4f7f\u3048\u307e\u3059\u3002\u30c4\u30fc\u30eb\u30c1\u30c3\u30d7\u306e\u4ee3\u66ff\u3084\u3001\u30ea\u30f3\u30afURL\u306e\u8868\u793a\u306a\u3069\u306b\u6d3b\u7528\u3055\u308c\u307e\u3059\u3002<\/p>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>\/* data\u5c5e\u6027\u3092\u30c4\u30fc\u30eb\u30c1\u30c3\u30d7\u4ee3\u308f\u308a\u306b\u8868\u793a *\/\n.tooltip {\n  position: relative;\n  cursor: pointer;\n}\n.tooltip::after {\n  content: attr(data-tip);\n  position: absolute;\n  bottom: 100%;\n  left: 50%;\n  transform: translateX(-50%);\n  background: #333;\n  color: #fff;\n  padding: 4px 10px;\n  border-radius: 4px;\n  white-space: nowrap;\n  font-size: 12px;\n  opacity: 0;\n  transition: opacity 0.2s;\n}\n.tooltip:hover::after {\n  opacity: 1;\n}<\/code><\/pre><\/div>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-markup\" data-lang=\"HTML\"><code>&lt;span class=\"tooltip\" data-tip=\"\u3053\u308c\u304c\u30c4\u30fc\u30eb\u30c1\u30c3\u30d7\u3067\u3059\"&gt;\u30db\u30d0\u30fc\u3057\u3066\u307f\u3066&lt;\/span&gt;<\/code><\/pre><\/div>\n\n\n<h2 class=\"wp-block-heading\">position \u3092\u4f7f\u3063\u3066\u88c5\u98fe\u3092\u81ea\u5728\u306b\u914d\u7f6e\u3059\u308b<\/h2>\n\n<p class=\"wp-block-paragraph\">\u7591\u4f3c\u8981\u7d20\u3092\u300c\u6d6e\u304b\u305b\u3066\u300d\u4efb\u610f\u306e\u4f4d\u7f6e\u306b\u7f6e\u304d\u305f\u3044\u5834\u5408\u306f\u3001<code>position: absolute<\/code> \u3092\u7591\u4f3c\u8981\u7d20\u306b\u8a2d\u5b9a\u3057\u3001\u89aa\u8981\u7d20\u306b <code>position: relative<\/code> \u3092\u4ed8\u3051\u307e\u3059\u3002\u3053\u308c\u306f\u983b\u51fa\u30d1\u30bf\u30fc\u30f3\u306a\u306e\u3067\u5fc5\u305a\u899a\u3048\u3066\u304f\u3060\u3055\u3044\u3002<\/p>\n\n\n<h3 class=\"wp-block-heading\">\u898b\u51fa\u3057\u306e\u5de6\u30dc\u30fc\u30c0\u30fc\u88c5\u98fe<\/h3>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>.heading-bar {\n  position: relative;\n  padding-left: 16px;\n  font-size: 20px;\n  font-weight: bold;\n  color: #51322b;\n}\n.heading-bar::before {\n  content: \"\";\n  position: absolute;\n  left: 0;\n  top: 0;\n  height: 100%;\n  width: 5px;\n  background: #d16176;\n  border-radius: 3px;\n}<\/code><\/pre><\/div>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-markup\" data-lang=\"HTML\"><code>&lt;h2 class=\"heading-bar\"&gt;\u30bb\u30af\u30b7\u30e7\u30f3\u30bf\u30a4\u30c8\u30eb&lt;\/h2&gt;<\/code><\/pre><\/div>\n\n\n<h3 class=\"wp-block-heading\">\u5439\u304d\u51fa\u3057\u306e\u4e09\u89d2\uff08::after \u3067\u4e09\u89d2\u5f62\u3092\u4f5c\u308b\uff09<\/h3>\n\n<p class=\"wp-block-paragraph\">CSS\u306e <code>border<\/code> \u3092\u4f7f\u3063\u305f\u4e09\u89d2\u5f62\u306f <code>::before<\/code> \/ <code>::after<\/code> \u306e\u4ee3\u8868\u7684\u306a\u6d3b\u7528\u4f8b\u3067\u3059\u3002border 3\u8fba\u3092 transparent \u306b\u3057\u30011\u8fba\u3060\u3051\u8272\u3092\u4ed8\u3051\u308b\u3068\u4e09\u89d2\u5f62\u306b\u306a\u308a\u307e\u3059\u3002<\/p>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>.balloon {\n  position: relative;\n  background: #EFBDB7;\n  border-radius: 8px;\n  padding: 12px 16px;\n  display: inline-block;\n  max-width: 280px;\n  color: #51322b;\n  font-size: 14px;\n}\n\/* \u4e0b\u5411\u304d\u4e09\u89d2 *\/\n.balloon::after {\n  content: \"\";\n  position: absolute;\n  bottom: -12px;\n  left: 20px;\n  border: 6px solid transparent;\n  border-top-color: #EFBDB7;\n}<\/code><\/pre><\/div>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-markup\" data-lang=\"HTML\"><code>&lt;div class=\"balloon\"&gt;\u3053\u3093\u306b\u3061\u306f\uff01\u7591\u4f3c\u8981\u7d20\u3067\u5439\u304d\u51fa\u3057\u3092\u4f5c\u308a\u307e\u3057\u305f\u3002&lt;\/div&gt;<\/code><\/pre><\/div>\n\n\n<h3 class=\"wp-block-heading\">\u4e0b\u7dda\u30a2\u30cb\u30e1\u30fc\u30b7\u30e7\u30f3\uff08\u30db\u30d0\u30fc\u30a8\u30d5\u30a7\u30af\u30c8\uff09<\/h3>\n\n<p class=\"wp-block-paragraph\">\u30ca\u30d3\u30b2\u30fc\u30b7\u30e7\u30f3\u30ea\u30f3\u30af\u306e\u30db\u30d0\u30fc\u6642\u306b\u4e0b\u7dda\u304c\u4f38\u3073\u308b\u30a8\u30d5\u30a7\u30af\u30c8\u3082\u3001\u7591\u4f3c\u8981\u7d20\u3068 <code>transition<\/code> \u3092\u7d44\u307f\u5408\u308f\u305b\u308b\u3068\u5b9f\u73fe\u3067\u304d\u307e\u3059\u3002<\/p>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>.hover-line {\n  position: relative;\n  display: inline-block;\n  text-decoration: none;\n  color: #51322b;\n  font-weight: bold;\n  padding-bottom: 4px;\n}\n.hover-line::after {\n  content: \"\";\n  position: absolute;\n  bottom: 0;\n  left: 0;\n  width: 0;\n  height: 2px;\n  background: #d16176;\n  transition: width 0.3s ease;\n}\n.hover-line:hover::after {\n  width: 100%;\n}<\/code><\/pre><\/div>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-markup\" data-lang=\"HTML\"><code>&lt;a href=\"#\" class=\"hover-line\"&gt;\u30db\u30d0\u30fc\u3059\u308b\u3068\u4e0b\u7dda\u304c\u4f38\u3073\u307e\u3059&lt;\/a&gt;<\/code><\/pre><\/div>\n\n\n<h2 class=\"wp-block-heading\">\u30a2\u30a4\u30b3\u30f3\u98a8\u88c5\u98fe\u30fb\u898b\u51fa\u3057\u30c7\u30b3\u30ec\u30fc\u30b7\u30e7\u30f3\uff08\u30b3\u30d4\u30da\u5b8c\u5168\u30b3\u30fc\u30c9\uff09<\/h2>\n\n<p class=\"wp-block-paragraph\">\u5b9f\u52d9\u3067\u305d\u306e\u307e\u307e\u4f7f\u3048\u308b\u30c7\u30b6\u30a4\u30f3\u30d1\u30bf\u30fc\u30f3\u3092\u307e\u3068\u3081\u307e\u3059\u3002\u3059\u3079\u3066\u30b3\u30d4\u30da\u3067\u52d5\u304d\u307e\u3059\u3002<\/p>\n\n\n<h3 class=\"wp-block-heading\">\u898b\u51fa\u3057\u306e\u524d\u5f8c\u306b\u7dda\u3092\u5165\u308c\u308b\uff08\u30bb\u30f3\u30bf\u30fc\u63c3\u3048\u30bf\u30a4\u30c8\u30eb\uff09<\/h3>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>.line-title {\n  display: flex;\n  align-items: center;\n  gap: 12px;\n  font-size: 22px;\n  font-weight: bold;\n  color: #51322b;\n}\n.line-title::before,\n.line-title::after {\n  content: \"\";\n  flex: 1;\n  height: 2px;\n  background: #d16176;\n}\n<\/code><\/pre><\/div>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-markup\" data-lang=\"HTML\"><code>&lt;h2 class=\"line-title\"&gt;\u30bf\u30a4\u30c8\u30eb&lt;\/h2&gt;<\/code><\/pre><\/div>\n\n\n<h3 class=\"wp-block-heading\">\u30ea\u30b9\u30c8\u30a2\u30a4\u30c6\u30e0\u306e\u30a2\u30a4\u30b3\u30f3\u4ee3\u66ff\uff08::before \u3067\u30c1\u30a7\u30c3\u30af\uff09<\/h3>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>.icon-list {\n  list-style: none;\n  padding-left: 0;\n}\n.icon-list li {\n  position: relative;\n  padding-left: 28px;\n  margin-bottom: 8px;\n  color: #51322b;\n  font-size: 15px;\n  line-height: 1.6;\n}\n.icon-list li::before {\n  content: \"\u2714\";\n  position: absolute;\n  left: 0;\n  top: 0;\n  color: #d16176;\n  font-weight: bold;\n}<\/code><\/pre><\/div>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-markup\" data-lang=\"HTML\"><code>&lt;ul class=\"icon-list\"&gt;\n  &lt;li&gt;HTML\u3092\u5909\u3048\u305a\u306b\u88c5\u98fe\u3067\u304d\u308b&lt;\/li&gt;\n  &lt;li&gt;CSS\u3060\u3051\u3067\u4e09\u89d2\u5f62\u304c\u4f5c\u308c\u308b&lt;\/li&gt;\n  &lt;li&gt;attr()\u3067\u30c7\u30fc\u30bf\u5c5e\u6027\u3092\u8868\u793a\u3067\u304d\u308b&lt;\/li&gt;\n&lt;\/ul&gt;<\/code><\/pre><\/div>\n\n\n<h3 class=\"wp-block-heading\">\u30e9\u30d9\u30eb\u4ed8\u304d\u898b\u51fa\u3057\uff08\u30ab\u30c6\u30b4\u30ea\u30fc\u30d0\u30c3\u30b8\uff09<\/h3>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>.badge-heading {\n  position: relative;\n  padding-top: 32px;\n  font-size: 20px;\n  font-weight: bold;\n  color: #51322b;\n}\n.badge-heading::before {\n  content: \"NEW\";\n  position: absolute;\n  top: 0;\n  left: 0;\n  background: #d16176;\n  color: #fff;\n  font-size: 11px;\n  font-weight: bold;\n  padding: 2px 8px;\n  border-radius: 4px;\n  letter-spacing: 0.05em;\n}<\/code><\/pre><\/div>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-markup\" data-lang=\"HTML\"><code>&lt;h3 class=\"badge-heading\"&gt;\u6700\u65b0\u306e\u304a\u77e5\u3089\u305b&lt;\/h3&gt;<\/code><\/pre><\/div>\n\n\n<h3 class=\"wp-block-heading\">\u5f15\u7528\u7b26\u30c7\u30b6\u30a4\u30f3\uff08blockquote\u88c5\u98fe\uff09<\/h3>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>.quote-block {\n  position: relative;\n  background: #fdf5f5;\n  border-radius: 8px;\n  padding: 24px 24px 24px 56px;\n  color: #51322b;\n  font-size: 15px;\n  line-height: 1.8;\n}\n.quote-block::before {\n  content: \"\u0081C\";\n  position: absolute;\n  left: 12px;\n  top: 8px;\n  font-size: 64px;\n  color: #EFBDB7;\n  line-height: 1;\n  font-family: Georgia, serif;\n}<\/code><\/pre><\/div>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-markup\" data-lang=\"HTML\"><code>&lt;blockquote class=\"quote-block\"&gt;\n  \u7591\u4f3c\u8981\u7d20\u3092\u4f7f\u3044\u3053\u306a\u3059\u3068\u3001HTML\u3092\u30b7\u30f3\u30d7\u30eb\u306b\u4fdd\u3061\u306a\u304c\u3089\u8c4a\u304b\u306a\u8868\u73fe\u304c\u53ef\u80fd\u306b\u306a\u308a\u307e\u3059\u3002\n&lt;\/blockquote&gt;<\/code><\/pre><\/div>\n\n\n<h2 class=\"wp-block-heading\">\u5358\u4e00\u30b3\u30ed\u30f3\uff08:before\uff09\u3068\u4e8c\u91cd\u30b3\u30ed\u30f3\uff08::before\uff09\u306e\u9055\u3044<\/h2>\n\n<p class=\"wp-block-paragraph\">\u7d50\u8ad6\u304b\u3089\u8a00\u3046\u3068\u3001<strong>\u52d5\u4f5c\u306f\u540c\u3058\u3067\u3059<\/strong>\u3002\u305f\u3060\u3057\u66f8\u304d\u65b9\u306e\u610f\u5473\u304c\u9055\u3044\u307e\u3059\u3002<\/p>\n\n<p class=\"wp-block-paragraph\">CSS2\u306e\u6642\u4ee3\u306f\u7591\u4f3c\u30af\u30e9\u30b9\uff08<code>:hover<\/code> \u306a\u3069\uff09\u3068\u7591\u4f3c\u8981\u7d20\uff08<code>:before<\/code> \u306a\u3069\uff09\u3092\u540c\u3058\u5358\u4e00\u30b3\u30ed\u30f3\u3067\u66f8\u3044\u3066\u3044\u307e\u3057\u305f\u3002CSS3\u304b\u3089\u7591\u4f3c\u8981\u7d20\u306f\u4e8c\u91cd\u30b3\u30ed\u30f3\uff08<code>::before<\/code>\uff09\u306b\u5909\u66f4\u3055\u308c\u3001\u7591\u4f3c\u30af\u30e9\u30b9\u3068\u533a\u5225\u3067\u304d\u308b\u3088\u3046\u306b\u306a\u308a\u307e\u3057\u305f\u3002<\/p>\n\n<figure class=\"wp-block-table\"><table><thead><tr><th>\u66f8\u304d\u65b9<\/th><th>CSS \u30d0\u30fc\u30b8\u30e7\u30f3<\/th><th>\u52d5\u4f5c<\/th><th>\u63a8\u5968<\/th><\/tr><\/thead><tbody><tr><td><code>:before<\/code><\/td><td>CSS2<\/td><td>\u52d5\u304f<\/td><td>\u975e\u63a8\u5968\uff08\u5f8c\u65b9\u4e92\u63db\u306e\u307f\uff09<\/td><\/tr><tr><td><code>::before<\/code><\/td><td>CSS3<\/td><td>\u52d5\u304f<\/td><td>\u63a8\u5968<\/td><\/tr><\/tbody><\/table><\/figure>\n\n<p class=\"wp-block-paragraph\">\u73fe\u4ee3\u306e\u30d6\u30e9\u30a6\u30b6\u306f\u4e21\u65b9\u5bfe\u5fdc\u3057\u3066\u3044\u307e\u3059\u304c\u3001\u65b0\u898f\u3067\u66f8\u304f\u30b3\u30fc\u30c9\u306f\u5fc5\u305a <code>::before<\/code> \/ <code>::after<\/code> \u306e\u4e8c\u91cd\u30b3\u30ed\u30f3\u8868\u8a18\u3092\u4f7f\u3044\u307e\u3057\u3087\u3046\u3002\u904e\u53bb\u306e\u30b3\u30fc\u30c9\u3092\u8aad\u3080\u3068\u304d\u306b <code>:before<\/code> \u304c\u51fa\u3066\u304d\u3066\u3082\u6016\u304c\u3089\u306a\u304f\u3066\u5927\u4e08\u592b\u3067\u3059\u3002<\/p>\n\n\n<h2 class=\"wp-block-heading\">\u3088\u304f\u3042\u308b\u5931\u6557\uff08\u8868\u793a\u3055\u308c\u306a\u3044\u539f\u56e0\u3068\u89e3\u6c7a\u7b56\uff09<\/h2>\n\n<p class=\"wp-block-paragraph\">\u7591\u4f3c\u8981\u7d20\u304c\u610f\u56f3\u901a\u308a\u306b\u8868\u793a\u3055\u308c\u306a\u3044\u3068\u304d\u3001\u539f\u56e0\u306f\u307b\u307c\u6c7a\u307e\u3063\u3066\u3044\u307e\u3059\u3002\u30c1\u30a7\u30c3\u30af\u30ea\u30b9\u30c8\u3068\u3057\u3066\u4f7f\u3063\u3066\u304f\u3060\u3055\u3044\u3002<\/p>\n\n\n<h3 class=\"wp-block-heading\">\u539f\u56e01: content \u30d7\u30ed\u30d1\u30c6\u30a3\u304c\u306a\u3044<\/h3>\n\n<p class=\"wp-block-paragraph\">\u6700\u3082\u591a\u3044\u539f\u56e0\u3067\u3059\u3002<code>content<\/code> \u3092\u7701\u7565\u3059\u308b\u3068\u7591\u4f3c\u8981\u7d20\u305d\u306e\u3082\u306e\u304c\u751f\u6210\u3055\u308c\u307e\u305b\u3093\u3002\u7a7a\u6587\u5b57\u3067\u3082\u5fc5\u305a\u66f8\u304f\u5fc5\u8981\u304c\u3042\u308a\u307e\u3059\u3002<\/p>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>\/* NG: content \u304c\u306a\u3044 *\/\n.box::before {\n  display: block;\n  width: 20px;\n  height: 20px;\n  background: red;\n}\n\n\/* OK: content: \"\" \u3092\u5fc5\u305a\u5165\u308c\u308b *\/\n.box::before {\n  content: \"\";\n  display: block;\n  width: 20px;\n  height: 20px;\n  background: red;\n}<\/code><\/pre><\/div>\n\n\n<h3 class=\"wp-block-heading\">\u539f\u56e02: \u89aa\u8981\u7d20\u306b position: relative \u304c\u306a\u3044<\/h3>\n\n<p class=\"wp-block-paragraph\"><code>position: absolute<\/code> \u3092\u4f7f\u3063\u305f\u7591\u4f3c\u8981\u7d20\u306f\u3001\u4e00\u756a\u8fd1\u3044 <code>position<\/code> \u304c\u8a2d\u5b9a\u3055\u308c\u305f\u7956\u5148\u8981\u7d20\u3092\u57fa\u6e96\u306b\u914d\u7f6e\u3055\u308c\u307e\u3059\u3002\u89aa\u8981\u7d20\u306b <code>position: relative<\/code> \u3092\u5fd8\u308c\u308b\u3068\u3001\u610f\u56f3\u3057\u306a\u3044\u5834\u6240\u306b\u8868\u793a\u3055\u308c\u307e\u3059\u3002<\/p>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>\/* NG: \u89aa\u306bposition\u304c\u306a\u3044 *\/\n.parent { }\n.parent::before {\n  content: \"\";\n  position: absolute;\n  top: 0; left: 0;\n}\n\n\/* OK: \u89aa\u306bposition: relative\u3092\u8ffd\u52a0 *\/\n.parent {\n  position: relative;\n}\n.parent::before {\n  content: \"\";\n  position: absolute;\n  top: 0; left: 0;\n}<\/code><\/pre><\/div>\n\n\n<h3 class=\"wp-block-heading\">\u539f\u56e03: display \u304c inline \u306e\u307e\u307e\u3067\u30b5\u30a4\u30ba\u304c\u52b9\u304b\u306a\u3044<\/h3>\n\n<p class=\"wp-block-paragraph\">\u7591\u4f3c\u8981\u7d20\u306e\u30c7\u30d5\u30a9\u30eb\u30c8\u306f <code>display: inline<\/code> \u3067\u3059\u3002<code>width<\/code> \/ <code>height<\/code> \u3092\u6307\u5b9a\u3057\u305f\u3044\u5834\u5408\u306f <code>display: block<\/code> \u307e\u305f\u306f <code>display: inline-block<\/code> \u306b\u5909\u66f4\u3059\u308b\u5fc5\u8981\u304c\u3042\u308a\u307e\u3059\u3002<\/p>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>\/* NG: \u30c7\u30d5\u30a9\u30eb\u30c8\u306einline\u306e\u307e\u307e\u30b5\u30a4\u30ba\u3092\u6307\u5b9a *\/\n.element::before {\n  content: \"\";\n  width: 100px;  \/* \u52b9\u304b\u306a\u3044 *\/\n  height: 4px;   \/* \u52b9\u304b\u306a\u3044 *\/\n}\n\n\/* OK: display \u3092\u5909\u66f4\u3059\u308b *\/\n.element::before {\n  content: \"\";\n  display: block;\n  width: 100px;\n  height: 4px;\n}<\/code><\/pre><\/div>\n\n\n<h3 class=\"wp-block-heading\">\u539f\u56e04: replaced element\uff08img\u30fbinput\uff09\u306b\u4f7f\u304a\u3046\u3068\u3057\u3066\u3044\u308b<\/h3>\n\n<p class=\"wp-block-paragraph\"><code>img<\/code>\u30fb<code>input<\/code>\u30fb<code>br<\/code>\u30fb<code>hr<\/code> \u306a\u3069\u306e\u7f6e\u63db\u8981\u7d20\uff08replaced element\uff09\u306b\u306f\u7591\u4f3c\u8981\u7d20\u3092\u4f7f\u3048\u307e\u305b\u3093\u3002\u3053\u308c\u3089\u306f\u30b3\u30f3\u30c6\u30f3\u30c4\u304c\u5916\u90e8\u30ea\u30bd\u30fc\u30b9\u3067\u6c7a\u307e\u308b\u305f\u3081\u3001CSS\u3067\u524d\u5f8c\u306b\u633f\u5165\u3059\u308b\u3053\u3068\u304c\u3067\u304d\u307e\u305b\u3093\u3002<\/p>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>\/* NG: img\u306b\u306f\u4f7f\u3048\u306a\u3044 *\/\nimg::before {\n  content: \"\u30a2\u30a4\u30b3\u30f3\";\n}\n\n\/* OK: img\u3092div\u3067\u5305\u3093\u3067\u305d\u3053\u306b\u4f7f\u3046 *\/\n.img-wrap {\n  position: relative;\n  display: inline-block;\n}\n.img-wrap::before {\n  content: \"NEW\";\n  position: absolute;\n  top: 8px;\n  left: 8px;\n  background: #d16176;\n  color: #fff;\n  padding: 2px 6px;\n  font-size: 11px;\n  border-radius: 4px;\n}<\/code><\/pre><\/div>\n\n\n<h2 class=\"wp-block-heading\">\u65e9\u898b\u8868\uff1a::before \u3068 ::after \u306e\u4e3b\u306a\u30d7\u30ed\u30d1\u30c6\u30a3<\/h2>\n\n<figure class=\"wp-block-table\"><table><thead><tr><th>\u30d7\u30ed\u30d1\u30c6\u30a3<\/th><th>\u3088\u304f\u4f7f\u3046\u5024<\/th><th>\u7528\u9014<\/th><\/tr><\/thead><tbody><tr><td><code>content<\/code><\/td><td><code>\"\"<\/code> \/ <code>\"\u6587\u5b57\u5217\"<\/code> \/ <code>attr(data-*)<\/code><\/td><td>\u7591\u4f3c\u8981\u7d20\u306e\u751f\u6210\uff08\u5fc5\u9808\uff09<\/td><\/tr><tr><td><code>display<\/code><\/td><td><code>block<\/code> \/ <code>inline-block<\/code> \/ <code>flex<\/code><\/td><td>\u30dc\u30c3\u30af\u30b9\u30e2\u30c7\u30eb\u3092\u6709\u52b9\u5316<\/td><\/tr><tr><td><code>position<\/code><\/td><td><code>absolute<\/code> \/ <code>relative<\/code><\/td><td>\u4efb\u610f\u306e\u4f4d\u7f6e\u3078\u914d\u7f6e<\/td><\/tr><tr><td><code>top \/ right \/ bottom \/ left<\/code><\/td><td>px \/ % \/ em<\/td><td>\u7d76\u5bfe\u914d\u7f6e\u306e\u5ea7\u6a19\u6307\u5b9a<\/td><\/tr><tr><td><code>width \/ height<\/code><\/td><td>px \/ % \/ vw<\/td><td>\u7591\u4f3c\u8981\u7d20\u306e\u30b5\u30a4\u30ba\u6307\u5b9a<\/td><\/tr><tr><td><code>background<\/code><\/td><td>\u8272 \/ \u30b0\u30e9\u30c7\u30fc\u30b7\u30e7\u30f3<\/td><td>\u88c5\u98fe\u306e\u8272\u3084\u80cc\u666f<\/td><\/tr><tr><td><code>border<\/code><\/td><td><code>solid transparent<\/code><\/td><td>\u4e09\u89d2\u5f62\u306e\u751f\u6210<\/td><\/tr><tr><td><code>transform<\/code><\/td><td><code>translateX(-50%)<\/code> \u7b49<\/td><td>\u30bb\u30f3\u30bf\u30ea\u30f3\u30b0\u3084\u56de\u8ee2<\/td><\/tr><tr><td><code>transition<\/code><\/td><td><code>all 0.3s ease<\/code><\/td><td>\u30a2\u30cb\u30e1\u30fc\u30b7\u30e7\u30f3<\/td><\/tr><tr><td><code>z-index<\/code><\/td><td>\u6574\u6570\u5024<\/td><td>\u91cd\u306a\u308a\u9806\u306e\u5236\u5fa1<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n<h2 class=\"wp-block-heading\">\u5b9f\u8df5\uff1a\u8907\u5408\u30b5\u30f3\u30d7\u30eb\uff08\u30dd\u30a4\u30f3\u30c8\u4ed8\u304d\u30ab\u30fc\u30c9\uff09<\/h2>\n\n<p class=\"wp-block-paragraph\">\u3053\u3053\u307e\u3067\u306e\u6280\u8853\u3092\u7d44\u307f\u5408\u308f\u305b\u305f\u5b9f\u8df5\u30b5\u30f3\u30d7\u30eb\u3067\u3059\u3002\u30ab\u30fc\u30c9\u306e\u5de6\u4e0a\u306b\u659c\u3081\u306e\u30ea\u30dc\u30f3\u88c5\u98fe\u3092\u4ed8\u3051\u307e\u3059\u3002<\/p>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>.card {\n  position: relative;\n  background: #fff;\n  border: 1px solid #EFBDB7;\n  border-radius: 12px;\n  padding: 24px;\n  max-width: 320px;\n  overflow: hidden;\n  box-shadow: 0 4px 12px rgba(81,50,43,0.08);\n}\n\n\/* \u5de6\u4e0a\u30b3\u30fc\u30ca\u30fc\u30ea\u30dc\u30f3 *\/\n.card::before {\n  content: \"PICK UP\";\n  position: absolute;\n  top: 18px;\n  left: -28px;\n  background: #d16176;\n  color: #fff;\n  font-size: 10px;\n  font-weight: bold;\n  letter-spacing: 0.08em;\n  padding: 4px 32px;\n  transform: rotate(-45deg);\n}\n\n\/* \u30ab\u30fc\u30c9\u4e0b\u90e8\u306e\u30a2\u30af\u30bb\u30f3\u30c8\u30e9\u30a4\u30f3 *\/\n.card::after {\n  content: \"\";\n  position: absolute;\n  bottom: 0;\n  left: 0;\n  width: 100%;\n  height: 4px;\n  background: linear-gradient(90deg, #d16176, #EFBDB7);\n}<\/code><\/pre><\/div>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-markup\" data-lang=\"HTML\"><code>&lt;div class=\"card\"&gt;\n  &lt;h3 style=\"margin-top:0;color:#51322b;\"&gt;\u304a\u3059\u3059\u3081\u8a18\u4e8b&lt;\/h3&gt;\n  &lt;p style=\"color:#51322b;font-size:14px;line-height:1.7;\"&gt;\n    \u7591\u4f3c\u8981\u7d20\u3092\u4f7f\u3048\u3070\u3001HTML\u3092\u6c5a\u3055\u305a\u306b\u30ea\u30c3\u30c1\u306a\u30c7\u30b6\u30a4\u30f3\u304c\u5b9f\u73fe\u3067\u304d\u307e\u3059\u3002\n  &lt;\/p&gt;\n&lt;\/div&gt;<\/code><\/pre><\/div>\n\n\n<h2 class=\"wp-block-heading\">\u5b9f\u8df5\uff1a\u30b9\u30c6\u30c3\u30d7\u30ea\u30b9\u30c8\uff08\u756a\u53f7\u4ed8\u304d\u88c5\u98fe\uff09<\/h2>\n\n<p class=\"wp-block-paragraph\">\u624b\u9806\u3092\u8aac\u660e\u3059\u308b\u969b\u306b\u4f7f\u3048\u308b\u30b9\u30c6\u30c3\u30d7\u30ea\u30b9\u30c8\u3067\u3059\u3002<code>counter()<\/code> \u3068\u7591\u4f3c\u8981\u7d20\u3092\u7d44\u307f\u5408\u308f\u305b\u3066\u3001\u81ea\u52d5\u63a1\u756a\u306e\u756a\u53f7\u30d0\u30c3\u30b8\u3092\u4f5c\u308a\u307e\u3059\u3002<\/p>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-css\" data-lang=\"CSS\"><code>.step-list {\n  list-style: none;\n  padding: 0;\n  counter-reset: step-counter;\n}\n.step-list li {\n  position: relative;\n  padding: 12px 12px 12px 56px;\n  margin-bottom: 12px;\n  background: #fdf5f5;\n  border-radius: 8px;\n  color: #51322b;\n  font-size: 15px;\n  line-height: 1.6;\n  counter-increment: step-counter;\n}\n.step-list li::before {\n  content: counter(step-counter);\n  position: absolute;\n  left: 12px;\n  top: 50%;\n  transform: translateY(-50%);\n  width: 30px;\n  height: 30px;\n  background: #d16176;\n  color: #fff;\n  font-weight: bold;\n  font-size: 14px;\n  border-radius: 50%;\n  display: flex;\n  align-items: center;\n  justify-content: center;\n}<\/code><\/pre><\/div>\n\n<div class=\"hcb_wrap\"><pre class=\"prism line-numbers lang-markup\" data-lang=\"HTML\"><code>&lt;ol class=\"step-list\"&gt;\n  &lt;li&gt;CSS\u30d5\u30a1\u30a4\u30eb\u306b\u7591\u4f3c\u8981\u7d20\u30bb\u30ec\u30af\u30bf\u30fc\u3092\u66f8\u304f&lt;\/li&gt;\n  &lt;li&gt;content \u30d7\u30ed\u30d1\u30c6\u30a3\u3092\u5fc5\u305a\u6307\u5b9a\u3059\u308b&lt;\/li&gt;\n  &lt;li&gt;position \u304c\u5fc5\u8981\u306a\u5834\u5408\u306f\u89aa\u8981\u7d20\u306b relative \u3092\u4ed8\u3051\u308b&lt;\/li&gt;\n  &lt;li&gt;display \u3092 block \u304b inline-block \u306b\u5909\u3048\u3066\u30b5\u30a4\u30ba\u3092\u52b9\u304b\u305b\u308b&lt;\/li&gt;\n&lt;\/ol&gt;<\/code><\/pre><\/div>\n\n\n<h2 class=\"wp-block-heading\">\u3088\u304f\u3042\u308b\u8cea\u554f\uff08FAQ\uff09<\/h2>\n\n<h3 class=\"wp-block-heading\">Q1. ::before \u3068 ::after \u306e\u3069\u3061\u3089\u3092\u4f7f\u3048\u3070\u3044\u3044\u306e\uff1f<\/h3>\n\n<p class=\"wp-block-paragraph\">\u8996\u899a\u7684\u306a\u88c5\u98fe\u3092\u300c\u8981\u7d20\u306e\u524d\uff08\u5de6\u30fb\u4e0a\uff09\u300d\u306b\u7f6e\u304d\u305f\u3044\u306a\u3089 <code>::before<\/code>\u3001\u300c\u8981\u7d20\u306e\u5f8c\uff08\u53f3\u30fb\u4e0b\uff09\u300d\u306b\u7f6e\u304d\u305f\u3044\u306a\u3089 <code>::after<\/code> \u3092\u4f7f\u3044\u307e\u3059\u3002\u305f\u3060\u3057 <code>position: absolute<\/code> \u3067\u914d\u7f6e\u3059\u308b\u5834\u5408\u306f\u3069\u3061\u3089\u3092\u4f7f\u3063\u3066\u3082 top\/left\/right\/bottom \u3067\u4efb\u610f\u306e\u4f4d\u7f6e\u306b\u7f6e\u3051\u308b\u306e\u3067\u3001\u305d\u306e\u5834\u5408\u306f\u3069\u3061\u3089\u3067\u3082\u69cb\u3044\u307e\u305b\u3093\u3002\u6163\u7fd2\u3068\u3057\u3066\u3001\u88c5\u98fe1\u3064\u76ee\u3092 <code>::before<\/code>\u30012\u3064\u76ee\u3092 <code>::after<\/code> \u306b\u5272\u308a\u5f53\u3066\u308b\u3053\u3068\u304c\u591a\u3044\u3067\u3059\u3002<\/p>\n\n<h3 class=\"wp-block-heading\">Q2. \u7591\u4f3c\u8981\u7d20\u306f\u4f55\u500b\u307e\u3067\u4f7f\u3048\u307e\u3059\u304b\uff1f<\/h3>\n\n<p class=\"wp-block-paragraph\">1\u3064\u306e\u30bb\u30ec\u30af\u30bf\u30fc\u306b\u5bfe\u3057\u3066 <code>::before<\/code> \u3068 <code>::after<\/code> \u306e\u5408\u8a082\u3064\u307e\u3067\u3067\u3059\u30023\u3064\u4ee5\u4e0a\u306e\u88c5\u98fe\u304c\u5fc5\u8981\u306a\u5834\u5408\u306f\u3001\u5b50\u8981\u7d20\u3092\u4f7f\u3046\u304b\u3001\u89aa\u30fb\u5b50\u30fb\u5b6b\u305d\u308c\u305e\u308c\u306b\u7591\u4f3c\u8981\u7d20\u3092\u5272\u308a\u5f53\u3066\u3066\u5bfe\u5fdc\u3057\u307e\u3059\u3002<\/p>\n\n<h3 class=\"wp-block-heading\">Q3. \u7591\u4f3c\u8981\u7d20\u306e\u30b9\u30bf\u30a4\u30eb\u306f JavaScript \u3067\u5909\u66f4\u3067\u304d\u307e\u3059\u304b\uff1f<\/h3>\n\n<p class=\"wp-block-paragraph\">JavaScript\u304b\u3089\u76f4\u63a5\u306f\u5909\u66f4\u3067\u304d\u307e\u305b\u3093\u3002\u7591\u4f3c\u8981\u7d20\u306fDOM\u306b\u5b58\u5728\u3057\u306a\u3044\u305f\u3081\u3067\u3059\u3002\u5bfe\u5fdc\u65b9\u6cd5\u306f2\u3064\u3042\u308a\u307e\u3059\u30021\u3064\u76ee\u306f\u89aa\u8981\u7d20\u306b\u30af\u30e9\u30b9\u3092\u4ed8\u3051\u66ff\u3048\u3001\u305d\u306e\u30af\u30e9\u30b9\u306b\u5bfe\u5fdc\u3057\u305f\u7591\u4f3c\u8981\u7d20\u30b9\u30bf\u30a4\u30eb\u3092CSS\u3067\u5b9a\u7fa9\u3059\u308b\u65b9\u6cd5\u30022\u3064\u76ee\u306f CSS \u30ab\u30b9\u30bf\u30e0\u30d7\u30ed\u30d1\u30c6\u30a3\uff08\u5909\u6570\uff09\u3092 JavaScript \u3067\u5909\u66f4\u3057\u3001\u7591\u4f3c\u8981\u7d20\u306e <code>content<\/code> \u3084\u8272\u3067\u53c2\u7167\u3059\u308b\u65b9\u6cd5\u3067\u3059\u3002<\/p>\n\n<h3 class=\"wp-block-heading\">Q4. content \u306b\u6539\u884c\u3092\u5165\u308c\u308b\u3053\u3068\u306f\u3067\u304d\u307e\u3059\u304b\uff1f<\/h3>\n\n<p class=\"wp-block-paragraph\">content \u30d7\u30ed\u30d1\u30c6\u30a3\u5185\u3067\u306f <code>\\A<\/code> \u304c\u6539\u884c\u30b3\u30fc\u30c9\u306b\u5bfe\u5fdc\u3057\u3066\u3044\u307e\u3059\u3002\u305f\u3060\u3057 <code>white-space: pre<\/code> \u3092\u5408\u308f\u305b\u3066\u6307\u5b9a\u3057\u306a\u3044\u3068\u6539\u884c\u304c\u53cd\u6620\u3055\u308c\u307e\u305b\u3093\u3002\u307e\u305f\u8996\u899a\u7684\u306a\u6539\u884c\u3088\u308a <code>display: block<\/code> \u3067\u5206\u5272\u3059\u308b\u307b\u3046\u304c\u30b7\u30f3\u30d7\u30eb\u306b\u7ba1\u7406\u3067\u304d\u307e\u3059\u3002<\/p>\n\n<h3 class=\"wp-block-heading\">Q5. \u30b9\u30af\u30ea\u30fc\u30f3\u30ea\u30fc\u30c0\u30fc\u306f\u7591\u4f3c\u8981\u7d20\u306e\u30c6\u30ad\u30b9\u30c8\u3092\u8aad\u307f\u4e0a\u3052\u307e\u3059\u304b\uff1f<\/h3>\n\n<p class=\"wp-block-paragraph\">\u30d6\u30e9\u30a6\u30b6\u30fb\u30b9\u30af\u30ea\u30fc\u30f3\u30ea\u30fc\u30c0\u30fc\u306e\u7d44\u307f\u5408\u308f\u305b\u306b\u3088\u3063\u3066\u7570\u306a\u308a\u307e\u3059\u304c\u3001\u591a\u304f\u306e\u74b0\u5883\u3067 <code>content<\/code> \u306b\u6307\u5b9a\u3057\u305f\u6587\u5b57\u5217\u306f\u8aad\u307f\u4e0a\u3052\u3089\u308c\u307e\u3059\u3002\u88c5\u98fe\u76ee\u7684\u306e\u8a18\u53f7\uff08\u300c\u203b\u300d\u300c\u2192\u300d\u306a\u3069\uff09\u304c\u8aad\u307f\u4e0a\u3052\u3089\u308c\u308b\u3068\u610f\u5473\u304c\u5909\u308f\u308b\u5834\u5408\u304c\u3042\u308b\u306e\u3067\u3001\u88c5\u98fe\u5c02\u7528\u306e\u7591\u4f3c\u8981\u7d20\u306b\u306f <code>content: \"\"<\/code>\uff08\u7a7a\u6587\u5b57\uff09\u3092\u4f7f\u3046\u304b\u3001<code>aria-hidden=\"true\"<\/code> \u3092\u89aa\u8981\u7d20\u306b\u4ed8\u3051\u308b\u65b9\u6cd5\u3092\u691c\u8a0e\u3057\u3066\u304f\u3060\u3055\u3044\u3002<\/p>\n\n\n\n<!-- withmedia-related -->\n<h2 class=\"wp-block-heading\">\u95a2\u9023\u8a18\u4e8b<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><a href=\"https:\/\/withcode.tech\/media\/css-triangle\/\">\u30102026\u5e74\u7248\u3011CSS\u3067\u4e09\u89d2\u5f62\u3092\u4f5c\u308b\u65b9\u6cd5\uff5cborder\u6280\u6cd5\u30fb\u5439\u304d\u51fa\u3057\u30fb\u77e2\u5370\u3092\u30b3\u30d4\u30da<\/a><\/li>\n<li><a href=\"https:\/\/withcode.tech\/media\/css-modern-ui-components-30\/\">\u3010\u30b3\u30d4\u30da\u53ef\u3011CSS\u3060\u3051\u3067\u4f5c\u308b\u30e2\u30c0\u30f3UI\u30d1\u30fc\u30c430\u9078\uff5c\u5b9f\u88c5\u30b3\u30fc\u30c9\u5168\u90e8\u8f09\u305b<\/a><\/li>\n<li><a href=\"https:\/\/withcode.tech\/media\/css-button-design-hover\/\">CSS\u30dc\u30bf\u30f3\u30c7\u30b6\u30a4\u30f330\u9078\uff5c\u30b3\u30d4\u30da\u3067\u4f7f\u3048\u308b\u304a\u3057\u3083\u308c\u306a\u30db\u30d0\u30fc\u30a8\u30d5\u30a7\u30af\u30c8\u96c6<\/a><\/li>\n<li><a href=\"https:\/\/withcode.tech\/media\/css-loading-animation\/\">CSS\u30ed\u30fc\u30c7\u30a3\u30f3\u30b0\u30a2\u30cb\u30e1\u30fc\u30b7\u30e7\u30f3\u96c6\uff5c\u30b3\u30d4\u30da\u3067\u5373\u4f7f\u3048\u308b\u5b9f\u88c5\u30b5\u30f3\u30d7\u30eb20<\/a><\/li>\n<li><a href=\"https:\/\/withcode.tech\/media\/css-color-change\/\">HTML\u3068CSS\u3067\u6587\u5b57\u8272\u3092\u5909\u3048\u308b\u65b9\u6cd5\uff5c\u521d\u5fc3\u8005\u5411\u3051\u5b8c\u5168\u30ac\u30a4\u30c9<\/a><\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\">CSS\u30fbWeb\u30c7\u30b6\u30a4\u30f3\u5b9f\u88c5\u306e\u7dcf\u307e\u3068\u3081<\/h2>\n\n\n\n<p 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