给moz-firefox下添加IE方法和属性

    */
    Event.prototype.__defineSetter__("returnValue",function(b){// 
        if(!b)this.preventDefault();
        return b;
        });
    Event.prototype.__defineSetter__("cancelBubble",function(b){// 设置或者检索当前事件句柄的层次冒泡
        if(b)this.stopPropagation();
        return b;
        });
    Event.prototype.__defineGetter__("srcElement",function(){
        var node=this.target;
        while(node.nodeType!=1)node=node.parentNode;
        return node;
        });
    Event.prototype.__defineGetter__("fromElement",function(){// 返回鼠标移出的源节点
        var node;
        if(this.type=="mouseover")
            node=this.relatedTarget;
        else if(this.type=="mouseout")
            node=this.target;
        if(!node)return;
        while(node.nodeType!=1)node=node.parentNode;
        return node;
        });
    Event.prototype.__defineGetter__("toElement",function(){// 返回鼠标移入的源节点
        var node;
        if(this.type=="mouseout")
            node=this.relatedTarget;
        else if(this.type=="mouseover")
            node=this.target;
        if(!node)return;
        while(node.nodeType!=1)node=node.parentNode;
        return node;
        });
    Event.prototype.__defineGetter__("offsetX",function(){
        return this.layerX;
        });
    Event.prototype.__defineGetter__("offsetY",function(){
        return this.layerY;