A common grammar-nazi pet peeve is the incorrect use of apostrophes.
Traditionally known as the greengrocer’s apostrophe because of signs like “Orange’s $1.99″, I think we could start calling it the newspapers’ apostrophe [note correct use of apostrophe] because of the amount of errors print editors seem to glance over.
Be aware of the its/it’s exception. You should only use an apostrophe with the word “it” when you want to indicate a contraction for “it is” or “it has”. Otherwise, its is one of the few words that indicates possession without an apostrophe. For example, “The dog is eating its bone”. This may seem confusing, but it follows the same pattern as other possessive pronouns: his, hers, its, yours, ours, theirs.
I’ll be the first to admit bad punctuation is a minor offense. However, doesn’t correct grammar make you feel nice and warm inside?
How to Use Apostrophes – [WikiHow]