[eva2000]

got it to work now with this

RewriteEngine on
RewriteRule ^/f([0-9]+)/?$ /forumdisplay.php?forumid=$1 [L]
RewriteRule ^/f([0-9]+)/s?$ /forumdisplay.php?forumid=$1 [L]
RewriteRule ^/t([0-9]+)\.html$ /showthread.php?threadid=$1 [L]
RewriteRule ^/t([0-9]+)/s([^/]?)\.html$ /showthread.php?threadid=$1&s=$2 [L]
RewriteRule ^/s([^/\?]0-9)+/$ /index.php?s=$1 [L]