Common mistakes in writing

They rear their ugly heads daily as I proofread and edit, worming their way into document after document as if sticking a tongue out at me goading, Catch me if you can. And I do catch them, day after day - mistakes I find so often they jump out at me from the page as if 3D.

Here's my top five:

1. Comma splices: It's amazing how many writers join two sentences together with a comma, and rather alarming how prevalent this has become in published books (take a look at this weekend's HP finale).
2. Missing/incorrect apostrophes: Did you notice the apostrophe in weekend's above? Many seem to feel the apostrophe is either optional, or something to plonk anywhere in the vicinity of the word in question.
3. Random capitals: I spend an impressive amount of my day decapitalising words.
4. Inconsistent styling: It's thirteen miles to London, but three lines later it's 15 days until Christmas.
5. Spellchecked nonsense: Just because that word is spelled correctly, doesn't mean it's the right word. This morning I found the following while proofreading a serious article on a church: The chap is a plaice for queer time (The chapel is a place for quiet time).