I don't seem to notice the advise one as much but the others I see all the time. When I first got online with all the different forums or whichever form of reading I was so caught up in people's poor grammar that I could hardly understand what they were trying to say. I guess I just got adjusted and decode the encoded messages now.
A spell checking program would only find if it were a word, not if it were the proper word. Microsoft word typically picks up on this sort of stuff though, I like to keep my usage of this at a minimum though. I find the more I use the auto correct and spell check the worse I begin spelling. I almost never spell check my posts, just if I know I misspelled a word and can't think of it off hand.
Splitting hares, that could get messy!
