function externalForms() {
 if (!document.getElementsByTagName) return;
 var forms = document.getElementsByTagName("form");
 for (var i=0; i<forms.length; i++) {
   var form = forms[i];
   if (form.getAttribute("name") &&
       form.getAttribute("rel") == "z")
     form.target = "_blank";
 }
}
window.onload = externalForms;