how to send a php's printed form trough ajax?

I have a navegator where I can search other users profile, the result of these searches are showed by an 'echo' with php... and these results have a form wich I need to send with ajax but no matter what I do I just can't stop the submit event...

the result of search it's something like...

        $mensaje .= '
        <form method="POST" action="users/myfile.php" id="compare">
        <input type="text" name="id_user" value="'.$id_user.'"/>
        <input type="submit"/>
        </form>';

echo $message;

and then I try to use ajax for loading a file without refreshing the page.

$('#compare').submit(function(e) {
    e.preventDefault();
    $.ajax({
        type: 'POST',
        url: $(this).attr('action'),
        data: $(this).serialize(),
        success: function(data) {
                            $('.profile-content').fadeIn('fast');
                            $('.profile-content').load('users/myfile.php');

        }
    })
    retu false;
}); 

using this, the result I got is the page just going to myfile.php instead of show what I need to show