///*回到顶部*/
        var layerFrom = ( document.compatMode.toLowerCase()=="css1compat" ) ? document.documentElement : document.body;
        function $(objID){return document.getElementById(objID);} 
		function doCompare() {
							var es = document.forms['compareForm'].elements;
							var n = 0;
							for (var i = 0; i < es.length; ++i) {
								var e = es[i];
								if (e.name == 'product_item_brand[]' && e.checked) { ++n; }
							}
							if(n < 2){alert("请至少选择两件商品进行对比");return false};
							if(n > 5){alert("最多选择五件商品进行对比");return false};
							document.forms['compareForm'].submit();
						}

		  function show_compare(id){
		                    var  spec_value=document.getElementById("spec_type_id").value;
							if(spec_value==""){
								spec_value=id
							}
							var es = document.forms['compareForm'].elements;
							var n = 0;
							var l = es.length;
							for (var i = 0; i < l; ++i) {
								var e = es[i];
								if (e.name == 'product_item_brand[]' && e.checked) { ++n; }
							}
							//alert(event.clientY+15);
							if (n > 0){
                              $("compare_layer").style.display='block';
							  $("compare_layer").style.top=layerFrom.scrollTop + event.clientY+10;
							  $("compare_layer").style.left=layerFrom.scrollLeft+ event.clientX-13;
                           }else{
                             $("compare_layer").style.display='none';
                          }
         }