简易遮罩层

//开启
if (是否开启？ture:false) {
   
    if($("#alertWindow").length > 0){
         $("body").find("#cover_div").remove();
    }
    var div = "<div id='cover_div' style='position:absolute;top:0px;left:0px;width:100%;height:100%;background:#fff;filter:Alpha(Opacity=10);/* IE */-moz-opacity:0.1;/* Moz + FF */opacity: 0.1;z-index:999999'><img src="+ctx+"/images/commons/loading6.gif style='position:absolute;top:48%;left:48%'></img></div>";
    $("body").append(div);
   }
//关闭
function clearcoverlayout(){
$("body").find("#cover_div").remove(); 
}