遮罩层（鼠标移到指定区域时，该区域显示，其他地方为半透明，移动时全部显示）

//使用方法//$(function () { setFloatBackgroundByID("adplay"); });//$(window).resize(function () { setFloatBackgroundByID("adplay"); });function setFloatBackgroundByID(id){    var $objId=$("#"+id);//整张大图片的id    $objId.css({"overflow":"hidden","position":"relative"});    var $html=$("<div class=\"flow\" style=\"width:"+$objId.width()+"px;height:"+$objId.height()+"px;left:0;top:0;display:none;position:absolute;opacity:0.5;z-index:1\">");     $objId.children().each(function(){   //为了防止append重复添加        if (!$objId.is(‘:has(".flow")‘) ) {             $objId.append($html);         }     })    var $mainImg=$objId.css("background-image"); //获取大图的url地址    var $divEach=$("div",$objId).not(".flow");    $divEach.css({"position":"absolute","overflow":"hidden","z-index":"100"});    $divEach.each(function(){        var $this=$(this);        $(this).css({"left":parseInt($this.attr("top"))+"px","top":parseInt($this.attr("left"))+"px"});        $(this).hover(function(){            var top=parseInt($(this).css("top"))+"px";  //定位            var left=parseInt($(this).css("left"))+"px";           var $Img=$mainImg + " -" + top + " -" + left; //注意top和left前面必须有一个空格，否则显示失败            //$this.css("background","none");            $html.css("display","");            $this.css({"background":$Img});

},function(){            $html.css("display","none")            $divEach.css("background","none");        })    })}下面是html代码//<div style="width: 960px; height: 508px; background: url(pic/swhw.jpg); overflow: hidden;" id="swimgbox">//    <a href="http://www.fsmjj.com/Product/Furniture/0a714b5c22144620815afc82b6069be0.shtml" target="_blank">//        <div style="width: 190px; height: 160px;" top="0" left="0">//        </div>//    </a><a href="http://www.fsmjj.com/Product/Furniture/18ea613c68af47ab9370a2886c3be9b4.shtml" target="_blank">//        <div style="width: 190px; height: 160px;" top="0" left="196">//        </div>//    </a>//</div>