title: When to use div id or div classes through an entire website
body: <p>Sorry for this basic over asked question but I feel I have something to add. </p>
  
  <p>I know id's are for elements which are only used once and classes are for elements which use it multiple times. But does this refer to a single page or the site as a whole? </p>
  
  <p>i.e If I were using a wrapper called main-wrapper which is only used once in the page but on every page of the website would this be an id or a class? I've been making them classes throughout this project and am curious if I need to go back and change it all.</p>