try enclosing it in a statement as such as
<!-- <? //UBBTREMARK -->
<!-- echo <<<UBBTPRINT -->
With Modifications from <a href="https://ubbdev.com" target="_blank">ThreadsDev.com</a>
<!-- UBBTPRINT; -->
if ($user[U_Number]){
<!-- echo <<<UBBTPRINT -->
googleaddsense
<!-- UBBTPRINT; -->
}
<!-- echo <<<UBBTPRINT -->
Visit the <a href="http://www.ubbcentral.com" target="_blank">Infopop</a> Support Forums
<!-- UBBTPRINT; -->
you will have to play with above of course but you get what I am doing.
