Quotation Mark, Period and Comma

Have been curious for very long time that whether period and comma should be inside or outside quotation mark.

The correct answer is, it depends on which side of Atlantic you are on.

From Wikipedia:

• “Carefree,” in general, means “free from care or anxiety.” (American practice)
• “Carefree”, in general, means “free from care or anxiety”. (British practice)

So far, my writing style is, unintentionally, British.