title: How to make an existing website themeable?
body: <p>I'm very new to this sort of thing, and I'm working on an existing production website. I've never styled a site from scratch, but what I'm trying to do is add some kind of functionality that allows users to customize their own themes, which will then be applied to the site.</p>
  
  <p>I apologize for the question being so bare, but what I'm looking for are different methods to make an existing web application themeable. I'm not entirely sure how to get more specific than that.</p>
  
  <p>Thanks in advance!</p>