Options -MultiViews
AddType text/xml .rng

RewriteEngine on
RewriteBase /rss1.1

RewriteCond %{DOCUMENT_ROOT}rss1.1/$1.cgi -f
RewriteRule ^([^\./]+)$ $1.cgi [L]

RewriteCond %{DOCUMENT_ROOT}rss1.1/$1.html -f
RewriteRule ^([^\./]+)$ $1.html [L]

RewriteCond %{DOCUMENT_ROOT}rss1.1/$1.png -f
RewriteRule ^([^\./]+)$ $1.png [L]