Sử dụng vừa CSS vừa HTML tạo trang 404 chuyên nghiệp hơn <style> #error-page { background-color:#e9e9e9; position:fixed !important; position:absolute; text-align:center; top:0; right:0; bottom:0; left:0; z-index:99999; } #error-inner { margin:11% auto; } #error-inner .box-404 { width:200px; height:200px; background:#21afa4; color:#fff; font-size:80px; line-height:200px; border-radius:10px; margin:0 auto 50px; position:relative; } #error-inner .box-404::after { content:" "; width:0; height:0; bottom:-8px; border-color:#21afa4 transparent transparent; border-style:solid; border-width:9px 9px 0; position:absolute; left:47%; } #error-inner h1 { text-transform:uppercase; } #error-inner p { line-height:0.7em; font-size:15px; } </style> <div id="error-page"> <div id="error-inner"> <div class="box-404">404</div> <h1>KHÔNG TÌM THẤ