I'll go with Sparteye's rule, too. My understanding of the origin of the rule is that in the old days periods and commas outside of quotes somehow managed to be in danger of breaking off or something stupid like that. That would explain why colons and semicolons could live safely outside the quotation marks. Certainly if you're writing for a computer instruction book of whatever kind, if you're using quotes to delimit something that has to be input to the computer you'd best not have anything inside the quotes that you don't want input.