function checklogincustomerform ( form )
{
  // ** START **
  if (form.custid.value == "") {
    alert( "Please enter a username." );
    form.custid.focus();
    return false;
  }
  if (form.pass.value == "") {
    alert( "Please enter a password." );
    form.pass.focus();
    return false;
  }
  if(isNaN(form.custid.value)) 
  { 
    alert("Please enter a valid username."); 
    return false; 
  }
  // ** END **
  return true ;
}