This page is meant to demonstrate what happens when a margin is set on the HTML tag itself. This is achieved by the user of some CSS in margintest.css which looks like this:
html { margin: 1em; }
This should put a 1em margin around the entire page which should not be clipped by the window at any point; nor should it cause the links to be offset etc.
Before if this is broken/a problem then the following link's hotspot within browser windows will be offset up/left by 1em and the window itself will not scroll properly to the bottom.
Here is a link to myself.