Slightly off topic, and a bit of an observation, but besides "your" and "you're," and "there," "their," and "they're," I think "ridiculous" and "definitely" are the most commonly misspelled words on message boards (that's a long-ass sentence). It's "definitely" "ridiculous."
I'm glad to see that I'm not the only one. Yeah, those two words are misspelled all of the time, even by those who rarely misspell. I won't name names, but I notice one of the best, most literate posters on this board misspelling "definitely" all the time. The way that I remember the correct spelling is easy: the root word of "definitely" is "finite" (de-finite-ly). You'd never spell "finite" as "finate," since it wouldn't sound right. So, just keep the correct spelling of "finite" in mind when spelling "definitely." Similarly, "ridiculous" comes from "ridicule," and you wouldn't spell out "redicule," would you? Anyways, the point is that I've found it quite helpful for spelling purposes (as well as usage purposes) to discover and and consider the etymology of words when writing.