This is for everyone that is using Joomla 1.7 (this fix may also work for Joomla 2.5). This file path is the same at: modules/mod_banners/tmpl/default.php, however the code is a lot different from Joomla 1.5. I have no idea why, but adding the center tag after the banneritem line like this: <div class="banneritem"><center> is what fixed it for me
. I'm going to try in Joomla 2.5 too to see if it fixes it there too.
Note: I tried changing the CSS in my templates, but none of that made a difference. This was the only thing below that worked for me.
finally centered the banners for me..
. This line of code seems to be a lot longer in Joomla 1.7 as well. This is the code for Joomla 1.7 and the center tag locations that finally fixed this issue for me
(note the change in center tag locations that I did on my site):