1. 方法一
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<script src="http://www.w3cschool.cn/jquery.js" type="text/javascript"></script>
<script type="text/javascript">
$(function(){
$(".btn").click(function(e){
e.stopPropagation();
$("#box").show();
});
$("#box").click(function(e){
e.stopPropagation();
});
document.onclick = function(){
$("#box").hide();
};
})
</script>
<style>
#box {width:300px;height:200px;border:1px solid #000;display:none}
</style>
</head>
<body>
<div id="box"></div>
<span class="btn">显示层</span>
</body>
</html>
2. 方法二
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文档</title>
<script src="http://www.w3cschool.cn/jquery.js" type="text/javascript"></script>
<script type="text/javascript">
$(function(){
$(".btn").click(function(){
$("#box").show();
return false;
});
$("#box").click(function(){
return false;
});
document.onclick = function(){
$("#box").hide();
};
})
</script>
<style>
#box {width:300px;height:200px;border:1px solid #000;display:none}
</style>
</head>
<body>
<div id="box"></div>
<span class="btn">显示层</span>
</body>
</html>
来源：http://bbs.blueidea.com/forum.php?mod=viewthread&tid=3056515&page=1#pid5427170
3. 判断元素是否被mouseover
$('#test').click(function() {
if ($('#hello').is(':hover')) {
alert('hello');
}
});
或者
if ($('#element:hover').length != 0) {
// do something ;)
}