FireFox下操作IFrame

//设置freetextbox的content
   var ed;
   //兼容IE/FireFox
   ed = document.all?eval("myTextBox_designEditor"):document.getElementById("myTextBox_designEditor").contentWindow ;//;
   ed.document.open();
   ed.document.write(objXml.getElementsByTagName("article")[0].firstChild.nodeValue);
   ed.document.close();