A Google Web Search Help thread has a group of searchers complaining about a single pixel that shows up when you click the next or previous buttons in Google Search. This only seems to show up for a second, when you click the next or previous button, but it also only shows up in Firefox 3.
Here are pictures:
As you can see, I circled in red, the pixel that seems to be really bugging some searchers.
Funny how the smallest little thing can really get on your nerves.
Forum discussion at Google Web Search Help.