dude, the first three are really close. Infact, one of those mistakes can easily be made if your apostrophe key is isn't very sensitive, or just doesn't always work for whatever reason. My shift key doesn't always work, and so I sometimes the first words to my sentences, and my proper nouns aren't capitalized, simply because I don't notice when they keyboard screws up.
Or if your keyboard has a quirk where it likes to put repeat letters, or if you simple double tap the O key on accident, you end up with "loose" instead of "lose".
Like I said, this is just about the least formal place for conversation (mostly because it about an unimportant subject, and essentially anonymous), and as a result, many don't really care enough about minor mistakes to go back and proof read their posts.
And language changes. Think about how many words we have now that weren't around in 1899, simply because the things the words represent weren't around back then. Grammar also changes, as does spelling and punctuation, though to a lesser degree. I'm sure that, were we able to talk with them, some one from 1692 would think our grammar horrendous.
