Without knowing anything about your site.
If you have some modifications to the basic code then that would be the templates.
If you are talking about appearance such as colors,highlights,banners, Etc then that would be the styles area .
Or HTML includes. But from 7.2 to 7.5.2 it should not be a styles issues unless something had a hiccup.
So possibly it is a code mod or a html include that is not working after the upgrade.
To get support here you may need to get a little more specific on what the problem is.
Probably just a issue with terms we use today that is not understood.
