A lot of people seem to have difficulty with punctuation. (Hint: "you're" and "your" are not interchangeable!) I guess it was too hard to pay attention during those boring high school classes where they taught such things. Anyway, if you want to make up for all those daydreaming hours, you can now learn punctuation in a fun way: comics!
How to use an apostrophe
And for a bonus, here is a comic about the neglected semicolon (my favorite punctuation mark!).
How to use a semicolon