[Zope] 'OFS/dtml' not needed

Hi, I have a Zope 2.5.1 on a Linux. If I rename the 'dtml' dir in 'OFS', my Zope has no problem working (after restarting or running in debug mode, of course). My problem started when I changed a dtml file in 'OFS/dtml' directory an the changes could not been seen. So this directory is not needed, where are those files keeped, what's happening?! Any ideea?! Thanks in advance, Best regards, Rares