OK! It works now ! Thanks !
I also found an easy way:
There is an option in the KDE menu for "Browse files as Root"or something like this, in system. From there you can delete and edit very easy the files.
After that just put your html page in var/www/ . and call apache.
In 5 minutes (including boot) you can put a webserver "on air" :>)

Another question now is : How do I enter as root if I start Knoppix in only text mode ?