We Americans just like to do things differently. One of those things is where we place some punctuation marks relative to quotation marks. In the U.S., periods and commas go inside quotation marks, like this:
I said, “Periods go inside quotation marks.”
“Commas do too,” I added.
The rest of the English-speaking world tends to disagree with us Yanks. But there is one rule of punctuation we all agree on — everyone except the writers and editors at Yahoo! News: Colons and semicolons always go outside quotation marks.