[users@httpd] warning message : what shall I do ?

[Etienne Loutrel]

hello

my apache server keeps sending me warning messages when I reload it on my
ubuntu server and I do not know how to fix that :

[Tue Aug 11 10:23:30 2009] [warn] NameVirtualHost *:80 has no VirtualHosts
[Tue Aug 11 10:23:30 2009] [warn] NameVirtualHost *:80 has no VirtualHosts
[Tue Aug 11 10:23:30 2009] [warn] NameVirtualHost *:80 has no VirtualHosts

any idea is warmly welcome

thanks

etienne