title: Injecting CSS into a website
body: <p>I'm creating a browser extension that'll allow you to adjust the CSS of a page.<br>
  Basically, if the user decides on a dark background with light text then that change should reflect across the site that they are viewing.<br>
  The reason for this is readability.<br>
  People with colour blindness and some vision related disabilities find it difficult to read some colours.</p>
  
  <p>There are several challenges with this.<br>
  I want to be able to change <code>background-color</code> elements to the chosen background colour and the <code>color</code> element to the chosen text-colour.  </p>
  
  <p>Obviously I have to account for complicated website layouts, and cater for those rules that are complicated, i.e.</p>
  
  <pre><code>#container div.note p
  </code></pre>
  
  <p>I can use Javascript in this, but no libraries like JQuery, so is there a way I can do this?</p>
  
  <p>Is there a way I can apply a CSS Stylesheet to the page that will override every background element and every color element in their stylesheet?</p>