I looked into this before, but for british window cleaning academy yellow pages advertising.
basically you pay to be in their little box which looks good. I think i was quoted about £85, and if I had of done it I would have been the only one in the bwca box in my yellow pages, which would have made me look good.
I never got around to doing it though, maybe next year. One job will pay for it and especially if you manage to be the only person in the box.