most annoying spelling mistakes

I'd like to cast my vote for "definately." It's astounding how often one sees "definitely" spelled that way.

realize - wrong

realise - right (wright) and others like it where the "s" is replaced by a "z"

Also, when vowels go missing as in "favourite" and spelled incorrectly as "favorite"

Now, that's annoying.

I have to agree with Juan that when realize is misspelled as realise and favorite is misspelled as favourite it's really annoying :P

I guess any word that one sees misspelled often is annoying. So for me some would be: separate spelled as seperate, and when people mix up your and you're, then and than, its and it's, there and their and they're, etc.

I didn't realize those annoyed you so much, Juan.

On the Internet:
From non-native English speakers: "hy" instead of "hi"; "heloo" instead of "hello" or "by" instead of " 'bye ".
From native English speakers: "it's" instead of "its" - "at it's right end"

''pronounciation'' instead of the correct ''pronunciation''. ''firey'' or ''firy'' instead of ''fiery''. ''mispell'' instead of ''misspell''.

''whimp'' instead of the correct ''wimp''.

Some people who have learned English as a second language, later they ignore their roots.

The "their", "there" and "they're" thing annoys me most.

And random apostrophes. (Which is bad because I still omit/include them arbitrarily at the end of really long days.)

The Unquestionable King of all Spelling Mistakes: "loose" for "lose"

''Banana's for sale'' instead of the correct ''bananas for sale''.

And what about Brittish?

To Juan: Someone could say missing Rs in pronunciation are as annoying as missing vowels in spelling.

My pet hate mis-spell is "sepErate" for separate. I see it so many times, even on official documents. How is it these errors pass spell-checks?

Maybe we should have a thread for favourite grammatical errors. In this case, mine is "less" for "fewer"..maybe it is becoming generally accepted now to say such things as "less books were borrowed last year". This is heard very often, even on the BBC. To me even the sound of it seems wrong. It's silly really, because no one would ever say "we had fewer snow than usual last winter" but it's the same error in reverse.