a:hover{margin-top：-10px;}没作用
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<style>
.nav{position:absolute;right:10px;border-bottom:10px solid #6cf;border-radius:5px;}
a{color:#000;width:100px;text-align: center;padding:10px;text-decoration:none;
font-family:sans-serif;
}
a:hover{background-color: #6cf;color:#ccc;border-radius:5px;margin-top:-10px;}
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