But if you don't know what we're talking about, it must have been a side effect of something else.
(Edit - for clarity, Manu posted while I was typing; "you" means Simon)
And a second edit - Manu is right. Just add that line to the CSS file (assuming you kept it). And while you're there, the existing CSS file is only needed for the zeros, and only if your iframe is above about 1000px