That's because you are missing the closing <div>. Also, never use http_location, as that will cause problems in https mode. Correct code is:
<div align="center"><a href="promo-codes-amp-hot-deals.html"><img src="{$ImagesDir}/giftgirl.gif" alt="" /></div>
<div align="center"><a href="promo-codes-amp-hot-deals.html"><img src="{$ImagesDir}/advergif.gif" alt="" /></div>