Periods in URLs

Does anybody have any information on how periods in URLs affects the ranking? More specifically, when the period is in the *.html files url.

For instance..

www.site.com/web-2.0.html

Or should it be './web-2-0.html'? web-20.html?

Is it possible that if I have periods other than before the file extension that visitors might get 404 errors???

 

Periods shouldn't be an issue at all.. Even spaces work (though they create a lot of trouble) ;-)