function fnGetCode(iframeId){                               
                var obj=null;
                if (document.all){//IE
                    obj = document.frames[iframeId].document;                
                    return($(obj).find(“.tx”).text());
                }else{//Firefox
                    obj = document.getElementById(iframeId).contentDocument;                                               
                    return($(obj).find(“code”).text());                                     
                }                               
            }

该函数可以根据iframeId来获取页面中嵌入的iframe中的xml的文本节点的内容。