title: Building an add-on to hide a <div> block on an HTML page
body: <p>There's a webpage with something annoying on it which I'd like to hide every time I visit it. I thought a good way to do this would be to make an add-on for Firefox.</p>
  
  <p>I've never done this before, and came across the web-based Firefox add-on builder. I'm not too sure where to go from here though. I know it should be quite easy to do this though. I suppose all I need to do is check if a  block with a certain id is used on a website, and if it is, then delete/hide it from my view.</p>
  
  <p>Is that the best way to do about this? If not, what do you suggest? If so, can you give me any tips to help me accomplish this?</p>