‘Rediculous’
It is ridiculous how many people spell ridiculous 'rediculous' these days. I must be reading the ridiculous spelling 'rediculous' dozens of times a day. English is my second language and I'm far away from claiming that I know it all, but if thousands of people keep making the same mistake on a regular basis it just makes my eyes bleed and my brain's spell-checker revolt. Same goes for 'definately' (wow, I really need to clean out the spam on that old page) and the horrific 'there' instead of 'their'.
Luckily, I just found that I'm not alone: