[Zope] Using ".." and "."

Everywhere I look on the tutorials, I see the use of URL0 (or 1 or 2 or whatever). Is there any disadvantages of just using "." when referencing? eg: <dtml-call "RESPONSE.redirect('..')"> to go from "users\update\update_user" document to the "users\" folder An interesting point is that if the document is the index_html, you would only use "." rather than ".." eg: <dtml-call "RESPONSE.redirect('.')"> to go from "users\update\" (the index_html of the update folder) to the "users\" folder So, is this a bad way to reference? Is there any advantage in the URLx referencing? Thanks :) SmileyChris