When we tap out our posts and comments in the blogosphere, sometimes there's a disconnect between what we intend to type and what ends up on the page. In the case of comments, if you don't catch it before you hit the Submit button, you're usually stuck with it. If it's bad enough, you might add a follow-up correction comment, possibly with a touch of self-deprecating humor (my usual approach).
I find that homonyms give me the most trouble. I use the words "there," "their" and "they're" enough that I usually slow down and examine them as soon as I realize I've typed them, just to make sure I got it right.
I've learned to cut others some slack on issues like this. It's all too easy to let one or two of these slip in here or there (notice how I put three more homonyms in this sentence?), and even proofreading your post before publishing it doesn't guarantee you'll find the error. So I don't rag on people when they make one of these mistakes.
But there are a couple of misspellings that have become quite prominent, and it's starting to get to me. The first has been around for a long time, and that's the confusion between "lose," which is a verb, and "loose," which is an adjective. "Looser" is a valid word, so when people type it when they intend to use "loser," no spellchecker barks at them about it. But make no mistake, people, that guy on the other side of the political spectrum that you hate is not a looser, he's a loser. Your insults lose a lot of their sting when you can't manage to use the correct words.
Another word that has been seeing a lot of misuse lately is "misled." That's the past tense of "mislead." I'm sure folks miss this one because "lead" can be pronounced two ways, "leed" and "led." But you know what, folks? The past tense of "lead" is "led," so the past tense of "mislead" is "misled."
I'm far from perfect myself, so I'm not going to start dissing bloggers and commenters who can't seem to get these right. I'm just saying it bugs me.