If it is the first element in your page, it should now be in the top left corner.
Does clouds.png have that whitespace in it? If so, that may be why you see a white space at the top/left.
Edit: Also, make sure you don't have any padding in your body or html elements. Often, people include this code:
at the top of their CSS, to automatically give all elements NO padding or margin as default. The * selector is known as the universal selector, meaning it applies to ALL elements.