It doesn't really annoy me. If I don't understand, I just simply ask them. :]
BUT... but if they go all like, "anz u no w8 i moin"... I get really annoyed and stop replying them. I mean, "n u know wat i mean" is better than that. :o
How I deal with them?
I make an offer they can't refuse... mwhahahahahaHAHAHAHAHAH!!!
Seriousyly though, I just ignore them.
I don't usually associate with people who type illiterately or in "slang."
If I can't understand or read it, I ask them to repeat themselves, only this time, use English.
I'm a very blunt person, so people usually write correctly when they talk to me. Sometimes, I won't say anything, I'll just stop talking to them. >,.,>
I used to do that but now I don't, so I don't really care and, besides, I've never really come across anyone who does talk like that.
It does get annoying after some time. I usually google what I don't understand.
I just ask them to use proper and correct spelling and grammar. As well as CORRECT capitalization.
As long as they do not over use slang/acronyms then I do not have a problem with it, but if they use it repetitively then I shall start to get annoyed.
That and also it does not make much sense to me, but again, not that much of a worry here.
UNLESS it's someone using slang on stories then i just close the tab because i can't get into something if the orthography is all messed up
i don't really care about using proper orthography online. how people type doesn't matter to me, i don't use proper grammar because the way i type on the internet doesn't say anything about me (except that im really lazy but w/e) it doesn't depict my intelligence, therefore making it a waste of time and effort.