Thanks for the extra information joliett89, this concerns me:
It was made to look that way to get people to pay more for redesign after buying the script.
Given you want to modify/re-design the script, and the terms of purchase specifically require further payment to do so, it sounds as if your plan would be a direct breach of the terms of sale/purchase.
I realise this is the reverse of your original approach, and doesn't answer the question you originally asked, but css styles html, so is last in the "chain" of delivering content to a user.
While we can help with the css, given your overall goal (assuming you are not prohibited from modifying the templates), I think it would be worthwhile asking about the best way to manage the site in the CMS (Content Management Systems) forum, or perhaps PHP - which seems to get lots of questions about Smarty itself.