Is this what the code should be in the PHP file?
<?
if (($sender_name == "") && ($sender_email == "") && ($message == "")) {
header("Location: http://localhost/simple_form.html");
exit;
}
$msg = "E-MAIL SENT FROM WWW SITE\n";
$msg .= "Sender's Name: $sender_name\n";
$msg .= "Sender's E-Mail: $sender_email\n";
$msg .= "Message: $message\n\n";
$to = "you@yourdoman.com";
$subject = "Web Site Feedback";
$mailheaders = "From: My Web Site <> \n";
$mailheaders .= "Reply-To: $sender_email\n\n";
mail($to, $subject, $msg, $mailheaders);
?>