We get an awful lot of stories in which fluorescent is misspelled florescent. Presumably partly because it's another one of those misspellings that a spellchecker won't catch, since florescence means "a state or period of flourishing."
I'm obliquely reminded to mention an interesting misspelling/mispronunciation: some years back, two friends of mine (who I went to high school with in Palo Alto) referred to someone's "sorrid past." They were really surprised to hear that the word they meant was spelled and pronounced sordid. (I may be misremembering; it's possible that one or both of them had already found out how it was really spelled, before we had this conversation.) We never did figure out where they'd both learned it as sorrid. And this came up again recently, when someone else who also grew up in Palo Alto casually used the word sorrid in conversation. (In this recent case the person did know the word sordid when I mentioned it, though.) So now I'm wondering if this is a Palo Alto thing, or if everyone learns it that way. Kinda like frustum, which even computer-graphics professionals tend to believe is spelled and pronounced frustrum.
My own primary example of that kind of thing was the word stasis. I encountered the word many times (usually in the phrase stasis field) as a kid, but I always read it as statis, presumably related to static and other words having to do with stillness. The first time I noticed the real spelling, probably in a Niven book, I thought smugly that it was a typo; I was shocked and distressed when I learned that I'd just been misreading it for years.
I think what all this comes back to is just how easy it is to perceive what you expect to perceive.
(And in accordance with Hartman's Law of Prescriptivist Retaliation, there was a typo in this entry for several years: "My own primarily example". Fixed in 2007.)