If it ain’t broke…
It worries me when I fix something and I don’t even understand why it’s broken in the first place. It almost certainly means I will have to go back and re-fix it later. It happens most often with style sheets and IE 6. “IE 6 is the bane of my existense”™
Pages where the content is in a table are clearing my floats when the shouldn’t be, only in IE 6. I don’t understand it, but the solution (for now) is to make all tables which are children of a certain element float:right;clear:right;. This works, but it still worries me because I fear there is something else deep in the site which will break because of this hack. Yet for now… it will stay.