<html><head lang="en"> <meta charset="UTF-8"> <title></title> <!-- 标签水平居中: 行内标签, 行内块级标签: text-align: center; 块级标签: margin: 0px auto; 标签垂直居中: line-height: 400px; --> <style> .test1{ background-color: red; 300px; height: 400px; text-align: center; line-height: 400px; } span{ background-color: purple; } .test2{ background-color: green; 90px; /*margin-left: auto;*/ /*margin-right: auto;*/ margin: 0px auto; text-align: center; } </style> </head> <body> <div class="test1"> <!--行内标签--> <span>12212</span> <!--行内-块级标签--> <!--<button>百度一下</button>--> <!--块级标签--> <!--<div class="test2">efwf</div>--> </div> </body></html>