function requestForm(form,callback) {
  try {
    var s=''+form.tagName;s=s.toUpperCase();
    while (form.parentNode && (s!="FORM")) {
       form=form.parentNode;
       s=''+form.tagName;s=s.toUpperCase();
   }
   if (!form.action) {
     return false;
   }
  } catch(e) {
    return false;
  }
  var qu='';
  for (var a=0;a<form.elements.length;a++) {
    if (form.elements[a].name!='') {
      if (qu!='') qu=qu+"&"+form.elements[a].name+"=";
      else qu=form.elements[a].name+"=";
      qu=qu+encodeURIComponent(form.elements[a].value);
    }
  }
  req = new XMLHttpRequest();
  req.open("post",form.action, true);
  req.setRequestHeader("Content-Type","application/x-www-form-urlencoded; charset=UTF8"); 
  req.onreadystatechange = function (aEvt) {
    if (req.readyState == 4) {
       if(req.status == 200) {
         //alert(req.responseText);
         //document.getElementById("resultado").innerHTML=req.responseText;
		 callback(req.responseText);
       }
       else
         alert("Error (" + req.status + ") loading page\n");
    }
  };
  req.send(qu); 
}