Hover a first link, you'll notice the 'a' block is is now from top till toe in gray. Go to a second link straigth away from the first. Now the background is only colored where no text is. When setting the ul margin to 0 something similar happens. Setting the margin back to nothing ('') doesn't get redrawn properly.

Bug reported: bug-217319
Status: Fixed in Opera 9 build 8692
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