I know why it doesn't work.
When say you place the html code for the ad like:
<img>ad.png</img> or whatever. When the Admin Panel places that code into the ad database it changes the < and > into
and
(Minus the red period) and that breaks the image so it doesn't display.
To fix it you have to manually access your database from say PHPMYADMIN and insert it there or set it up so the text box doesn't convert html characters.