function validate(form){
 
  var error = "";
  //for each form element
  for(var i=0; i<form.length; i++){
   var element = form[i];
   //if required
   if(element.getAttribute("required") == "yes"){
    //if form element if empty
    if(!valid(element.value,element.getAttribute("validate")))
     error += element.getAttribute("message") + "\r\n"; 
   }
  }
  if(error != ""){
   alert(error);
   document.formSubmit = false;
  }
  else
   document.formSubmit = true;
 } 
 
 function valid(value,type){
  if(value == "")
   return false;
   
  switch(type){
   case "int":
    if(isNaN(parseInt(value)))
     return false;
    break;
   case "float":
    if(isNaN(parseFloat(value)))
     return false;
    break;
   case "email":
    var p = value.indexOf('@');
    if(p<1 || p==(value.length-1))
     return false;
   default://string
    break;
  }
  return true;
 }