Anyhoo... according to the wonderful french.about.com site, French does have slightly different punctuation to English.
I already knew about the decimal point thing, where a full stop/period would not be used and a comma would be used instead. eg - 1.5kg of tomatoes = 1,5 kg de tomates.
The main differences that became obvious to me was that there is a space before a colon (:), a semi-colon (;), an exclamation mark (!) and a question mark (?). Also that the quotation marks (" ") are not used, but the 'guillemets' instead. ( « » )
More explained here and how to type them in HTML.