function contact(contact_info) {
  if (contact_info.first.value == "")
  {
    alert("Please enter a valid first name.");
    contact_info.first.focus();
    return(false);
  }

  if (contact_info.last.value == "")
  {
    alert("Please enter a valid last name.");
    contact_info.last.focus();
    return(false);
  }

  var email=contact_info.email.value;
  if (email.indexOf(' ')==-1 
    && 0<email.indexOf('@')
    && email.indexOf('@')+1 < email.length
  ) return true;
    else alert ('Invalid email address!')
  return false;

}