Does the comma go inside or outside of a closing quotation mark? The difference is less than a milimeter, but there is an ocean of difference to an editor. The Atlantic Ocean, to be specific. This is one of those things, like whether to put a u in color or spell gray with an e, that distinguishes British from American English usage.
First, let’s answer the question. In the United States, the comma goes inside the quotation mark. The period goes inside the quotation mark too. No logic or thinking is involved. You just put it on the inside, like this—she said, “Don’t even think about it,” then slammed the door. And this—He gave one good reason: “Because I said so.”
If it sounds like a fight, that is because in business and editorial offices this often does become a fight, because it is an arbitrary-seeming style rule. However, it is important for consistency, which is the mark of a high-quality publication or a well-constructed business document. And the tradition in American publishing is to punctuate quotations this way.
Here are the U.S. rules for other punctuation with quotation marks:
Colons and semicolons always go outside a closing quotation mark.
Question marks and exclamation points go either on the outside or the inside of the quotation mark, depending on whether the punctuation is part of the quote or not. Thus:
He asked, “How do you punctuate a question?” (The quote is actually a question, so the question mark is part of the quote.)
She shouted, “No way!”(The exclamation point is part of the quote.)
Did he say, “I don’t know”? (The quote is not a question, so the question mark does not go inside the quotation mark. The overall sentence is a question, so the question mark goes at the very end, after the closing quotation mark.)
Did she ask, “Where is the library?” (When both the quote and the overall sentence are questions, you arbitrarily opt for inside.)
Now that we have looked at the rules, it is time to look at the exception. In text that is specifying exactly what to type in something like a computer programming language or a URL, you do not put the comma or period inside the quote: Now type “http://www.iconlogic.com”, which is the web address of our company.