If you think a comma goes before a closing quotation mark, and never after, you might just be an American. ‘Cause that’s the way we punctuate here in the U. S. of A. If you think it goes after, then you might be thinking like the rest of the English-speaking world and like this Yahoo! Beauty editor:
In the U.S., two punctuation marks always go before a closing quotation mark: comma and period.