I found the problem when I ran the Wiki with Mozilla Firefox. It was actually a problem with the autolink2 plugin which caused the mistake. The mistake war described at the autolink page as the following (the information is copied from the autolink page,
http://www.dokuwiki.org/plugin:autolink2) :
If you get the warning
Call-time pass-by-reference has been deprecated;
If you would like to pass it by reference, modify the declaration of [runtime function name](). etc. etc.
change in admin.php line 123
return search_regex(&$data,$base,$file,$reg,$words);
to
return search_regex($data,$base,$file,$reg,$words);