I will correct any misplaced grammar (including punctuation) or badly spelt words. As you may have read 92% of people stop reading your article once they come across bad grammar. So, whether it's a business proposal or an advertisement, make sure you know that those 92% of people will read till the end. I will correct up to 20 pages of writing. Studying english at Oxford and being editor on a magazine I know grammar like the back of my hand.