function checkform ( form )
{

  
  if (form.username.value == "") {
    alert( "Please enter your username." );
    form.first_name.focus();
    return false ;
  }
  
  
   if (form.password.value == "") {
    alert( "Please enter your password." );
    form.last_name.focus();
    return false ;
  }
 
  
  return true ;
}