In Sweden manhole covers are marked with either 'k' or 'a'. Some people believe that the “k” represents kärlek (love) and the “a” signifies avbruten (broken love). If you step on too many a covers your love life is likely to end up in the sewer (yeah, yeah, I know).
Here's a link.
What superstitions govern your life? And if you say you're not superstitious you'd better tap on wood to make sure no demons heard you say it.