[Greasemonkey] how to get elements in iframe

[jinqi.yin]

 i try to get elements in iframe , it doesn't work.
the code seems like this .
function outlinksframe(){
 if(!document.getElementsByTagName("iframe")) return;
 var iframes = document.getElementsByTagName("iframe");
 for(var j=0; j<iframes.length; j++){
 if(iframes[j]){
 if(iframes[j].getElementsByTagName("form")){
 var form11 = iframes[j].getElementsByTagName("form");
 form11.action = "";
 form11.target = "_blank";
 alert("in loop:" + form11.target + "\n" + form11.method);
 }
 }
 }
}
outlinksframe();
  yours
jinqi