jquery中的mousewheel事件，注意 以下代码可能不兼容firefox
<!doctype html>
<html>
<head>
<script type="text/javascript" src="http://www.qmsxw.com/js/jquery-1.12.0.min.js"></script>
<meta charset="utf-8">
<title>无标题文档</title>
</head>
<body>
<script>
$(document).on('mousewheel', function(e) {
//var md=e.originalEvent.wheelDelta
e.originalEvent.wheelDelta<0?$(".head").animate({height:"30px"}):$(".head").animate({height:"600px"},1000)
});
</script>
<div id="msg" style="position:fixed;top:0; background:#573C3C"></div>
<div class="top"></div>
<div class="bannar"></div>
<div class="head" style="background:#191212;height:600px;">saassaas</div>
</body>
</html>
