H5+CSS3：鼠标悬浮时出现下拉框

[我真的是too菜]

H5:
<a href="#" class="yi">aa
<div class="chu"></div>
</a>

CSS3：
a{
display: inline-block;
}
.yi:hover .chu{
display: block;
}
.chu{
display: none;
width: 100px;
height: 100px;
background-color: #ddd;
}

[shuxhan]

?????什么