function validate(tf)
{

    var msg = '';
    submitok=true;

   if(tf.email.value.length !=0){
      if(tf.email.value.indexOf("@") == -1){
         msg += "Please enter a valid email address.<br/>";
         submitok = false;
      } 
      else if(tf.email.value.length !=0){
        if(tf.email.value.indexOf(".") == -1){
           msg += "Please enter a valid email address.<br/>";
           submitok = false;
        } 
      }  
   }
   else
   {
        submitok=false;
        msg += "Please enter a valid email address.<br/>";
   }
  
   if(!submitok){
      document.getElementById('errormsg').innerHTML = msg;

   }
   return submitok;
}