Suppose you want to put the contents of a page right up against the edges of the browser’s viewport. While you can force this using absolute positioning, there is a more elegant solution.
The reason why content doesn’t start right at the top-left edge is because of margins. Some assume that if you don’t set the top and left margins for theelement, that it’s the equivalent to setting them to 0px. But this isn’t true.
In fact, browsers have built-in stylesheets that cause theelement to display as if you had set margins. For example, IE actually defaults the left margin to 10px and the top margin to 15px.
To override these defaults, use the following code: