title: Appending fixed iframe at top of any (unknown) page - how to push the contents down?
body: <p>I'm creating a chrome extension which can append an iframe with a toolbar on top of any page on certain circumstances. The iframe is fixed at the top.</p>
  
  <p>Obviously I don't want to destroy the original content so I need to push it down. But since it can be any website, I need to find a good and generic way to do this. </p>
  
  <p>I tried to set a margin on the body or to create a static element with an exact height but turns out that it can't work if there are elements that are fixed or absolute positioned (like a header for example).</p>
  
  <p>Well, I could set a margin on the body and also push all other absolute or fixed elements down by the same height, but this would lead into going through all elements of that page to find the fixed or absolute ones - on any page load. It get's even worse if they have relative positions like <em>margin-top: 50%</em> or something.</p>
  
  <p>So, what is the best way to achieve this?</p>