My pet peeves are mainly grammar-related.
1. I'm okay with people occasionally mixing up words, but if you mess up something as simple as "quite" (no, it's not "quiet," you fools) "whiny" ("whinny" is what horses use as their sound), or moot ("mute" is talking about an inability to make sound, you idiots!), you should be taking middle school spelling courses instead of fucking around on the Internet. Or, better yet, look them the fuck up!
2. Caps Lock pisses me off, and I only use it when it's in characterization. Yes, we get that you want to share something. You don't need to do the Internet equivalent of yelling at the top of your lungs. That's just rude as fuck.
3. Failing to capitalize certain letters and failing to add punctuation or apostrophes is inexcusable unless you are on Twitter - and even that isn't really an excuse where you can't capitalize the fucking "I" in a sentence!
4. Please, for the love of fate, learn the difference between "your" and "you're." I'm sick and fucking tired of these morons failing to understand something that's taught in basic elementary. The only reason a person should be allowed to struggle with them should be if they are literally coming into an English speaking country for the first time. That alone doesn't give them the right to botch something so simple.
And...well, that's my ranting. Thanks for hearing me out.