Information Pop-Up (like Vbulletin)

I am looking for code similar to what Vbulletin and other forums use. It is the small banner/box that appears at the VERY top of the page thats says something like "Register Today."

Actually, it may be some sort of Internet Explored code as well, as my windows system shows a default "alert" icon.

Thanks in advance!

 

<?php

if(isset($HTTP_COOKIE_VARS["loggedin"]) != TRUE)
{
die ("<a href='register.php'>Register</a> today!");
}

?>

PHP:

Now that's assuming when they log in you set a cookie called "loggedin".