#5 No Follow Cooperative: June, 2005
It’s always a surprise to see competitors working closely on something that benefits everyone, but that’s exactly what happened in June of 2005. That’s when Google convinced Yahoo and MSN to go along with their crazy follow/no-follow scheme.
The no-follow link was designed to be the big gun in the war against link spam. It’s been pretty effective, but seven years later, plenty of folks still don’t really understand how it works, or that it exists at all.