It doesn't really make me angry, but it does make me take the poster less seriously. And, granted, there are some exceptions: if someone makes a good post and spells "unfortunately&qu ot; wrong, I can take that--while common, it's a big word and I misspell it all the time. However wen yor post looks lik this.......... It makes me not even want to read it. As long as you clearly put at least a little
effort forth, it doesn't bother me a ton.
Although I should note that the one exception to this is "alot" instead of "a lot." Mostly because it makes me think of this.