页面设置遮罩层

<style>
　　.mask {position:absolute;background:rgba(0,0,0,0.2) url(../image/loading.png) no-repeat center center;z-index: 9999; opacity: 0.5;-moz-opacity:0.5;}
</style>

<div ></div>

数据加载之前显示遮罩层

　　$("#mask").css("height",$(document).height());
　　$("#mask").css("width",$(document).width());
　　$("#mask").show();