they do but i cant be bothered to use it on a forum, however if i were writing a letter my capitalization, punctuation and grammer would be used accordingly
No it wouldn't, and if it were you would have to look it up. There's no excuse since if you knew the proper usage it would be automatic. For instance if you knew the proper usage of 'there' you would have to try to use the improper 'they're' or 'their.' The "it's just a forum" or "I know which is correct but I just don't care" excuses hold no weight.