As many WP users have found, WP enables stat tracking by loading a small image of a smiley (called Angela) at the bottom of the page. For most users Angela is not troublesome, but in the event that you need to hide her, you can do so via the Custom CSS upgrade, without adversely affecting your stats traffic by adding the following code:
[sourcecode language='css']
img#wpstats {
visibility:hidden;
}
[/sourcecode]
This will hide the image as long as the css file loads, but should not interfere with the stat tracker as the image is still theoretically loading behind the style.