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div内容居中 <!-- DESKTOP NAVIGATION --> <nav class="top-bar"> <div class="wrap"> <div class="top-bar-left"> <h3>site title</h3> </div> <div class="top-bar-right"> <ul class="menu"> <li><input type="search" placeholder="Search"></li> <li><button type="button" class="button">Search</button></li> </ul> </div> </div> </nav> .wrap{ width: 90%; margin: 0 auto; max-width: 1000px; } 1.用百分号的好处就是能够实时计算 2.margin用于