What is the meaning of 'no acceptable variant' ERROR message?
Inside the httpd.conf file there are the following lines of code: 

AddLanguage de .de
AddLanguage en .en

# LanguagePriority allows you to give precedence to some languages
# in case of a tie during content negotiation.
#
# Just list the languages in decreasing order of preference. We have
# more or less alphabetized them here. You probably want to change this.
#
LanguagePriority en de

# ForceLanguagePriority allows you to serve a result page rather than
# MULTIPLE CHOICES (Prefer) [in case of a tie] or NOT ACCEPTABLE (Fallback)
# [in case no accepted languages matched the available variants]
#
ForceLanguagePriority Prefer Fallback


You should understand what it means and how you can alter its functions. Maybe you ask an Apache Server Guru ;)