Надо вырезать из урла символы

Robin_Bad:
вам на каком этапе их преобразовать-то требуется? если просто поменять ссылки на выводе, то что-то на основе варианта Stek подойдёт. или же вам нужен mod_rewrite (и аналоги), чтобы при переходе на URL вида http://site.com/topic-t242.html пользователя перекидывало на http://site.com/topic242.html?

Options +FollowSymLinks
RewriteEngine On
RewriteCond %{HTTP_HOST} ^site\.ru$ [NC]
RewriteRule ^(.*)$ http://www.site.ru/$1 [R=301,L]

# Lines That should already be in your .htacess
<Files "config.php">
Order Allow,Deny
Deny from All
</Files>
<Files "common.php">
Order Allow,Deny
Deny from All
</Files>

# You may need to un-comment the following lines
# Options +FollowSymlinks
# To make sure that rewritten dir or file (/|.html) will not load dir.php in case it exist
# Options -MultiViews
# REMEBER YOU ONLY NEED TO STARD MOD REWRITE ONCE
RewriteEngine On
# Uncomment the statement below if you want to make use of
# HTTP authentication and it does not already work.
# This could be required if you are for example using PHP via Apache CGI.
# RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization},L]
# REWRITE BASE
RewriteBase /
# HERE IS A GOOD PLACE TO FORCE CANONICAL DOMAIN
# RewriteCond %{HTTP_HOST} !^site\.site\.ru$ [NC]
# RewriteRule ^(.*)$ http://www.site.ru/$1 [QSA,L,R=301]

# DO NOT GO FURTHER IF THE REQUESTED FILE / DIR DOES EXISTS
RewriteCond %{REQUEST_FILENAME} -f
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule . - [L]
#####################################################
# PHPBB SEO REWRITE RULES ALL MODES
#####################################################
# AUTHOR : dcz www.phpbb-seo.com
# STARTED : 01/2006
#################################
# FORUMS PAGES
###############
# FORUM INDEX REWRITERULE WOULD STAND HERE IF USED. "forum" REQUIRES TO BE SET AS FORUM INDEX
# RewriteRule ^forum\.html$ /index.php [QSA,L,NC]
# FORUM ALL MODES
RewriteRule ^(forum|[a-z0-9_-]*-f)([0-9]+)(-([0-9]+))?\.html$ /viewforum.php?f=$2&start=$4 [QSA,L,NC]
# TOPIC WITH VIRTUAL FOLDER ALL MODES
RewriteRule ^(forum|[a-z0-9_-]*-f)([0-9]+)/(topic|[a-z0-9_-]*-t)([0-9]+)(-([0-9]+))?\.html$ /viewtopic.php?f=$2&t=$4&start=$6 [QSA,L,NC]
# GLOBAL ANNOUNCES WITH VIRTUAL FOLDER ALL MODES
RewriteRule ^announces/(topic|[a-z0-9_-]*-t)([0-9]+)(-([0-9]+))?\.html$ /viewtopic.php?t=$2&start=$4 [QSA,L,NC]
# TOPIC WITHOUT FORUM ID & DELIM ALL MODES
RewriteRule ^([a-z0-9_-]*)/?(topic|[a-z0-9_-]*-t)([0-9]+)(-([0-9]+))?\.html$ /viewtopic.php?forum_uri=$1&t=$3&start=$5 [QSA,L,NC]
# PHPBB FILES ALL MODES
RewriteRule ^resources/[a-z0-9_-]+/(thumb/)?([0-9]+)$ /download/file.php?id=$2&t=$1 [QSA,L,NC]
# PROFILES ALL MODES WITH ID
RewriteRule ^(member|[a-z0-9_-]*-u)([0-9]+)\.html$ /memberlist.php?mode=viewprofile&u=$2 [QSA,L,NC]
# USER MESSAGES ALL MODES WITH ID
RewriteRule ^(member|[a-z0-9_-]*-u)([0-9]+)-(topics|posts)(-([0-9]+))?\.html$ /search.php?author_id=$2&sr=$3&start=$5 [QSA,L,NC]
# GROUPS ALL MODES
RewriteRule ^(group|[a-z0-9_-]*-g)([0-9]+)(-([0-9]+))?\.html$ /memberlist.php?mode=group&g=$2&start=$4 [QSA,L,NC]
# POST
RewriteRule ^post([0-9]+)\.html$ /viewtopic.php?p=$1 [QSA,L,NC]
# ACTIVE TOPICS
RewriteRule ^active-topics(-([0-9]+))?\.html$ /search.php?search_id=active_topics&start=$2&sr=topics [QSA,L,NC]
# UNANSWERED TOPICS
RewriteRule ^unanswered(-([0-9]+))?\.html$ /search.php?search_id=unanswered&start=$2&sr=topics [QSA,L,NC]
# NEW POSTS
RewriteRule ^newposts(-([0-9]+))?\.html$ /search.php?search_id=newposts&start=$2&sr=topics [QSA,L,NC]
# UNREAD POSTS
RewriteRule ^unreadposts(-([0-9]+))?\.html$ /search.php?search_id=unreadposts&start=$2 [QSA,L,NC]
# THE TEAM
RewriteRule ^the-team\.html$ /memberlist.php?mode=leaders [QSA,L,NC]
# HERE IS A GOOD PLACE TO ADD OTHER PHPBB RELATED REWRITERULES

# FORUM WITHOUT ID & DELIM ALL MODES (SAME DELIM)
# THESE FOUR LINES MUST BE LOCATED AT THE END OF YOUR HTACCESS TO WORK PROPERLY
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^([a-z0-9_-]+)(-([0-9]+))\.html$ /viewforum.php?forum_uri=$1&start=$3 [QSA,L,NC]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^([a-z0-9_-]+)\.html$ /viewforum.php?forum_uri=$1 [QSA,L,NC]
# FIX RELATIVE PATHS : FILES
RewriteRule ^.+/(style\.php|ucp\.php|mcp\.php|faq\.php|download/file.php)$ /$1 [QSA,L,NC,R=301]
# FIX RELATIVE PATHS : IMAGES
RewriteRule ^.+/(styles/.*|images/.*)/$ /$1 [QSA,L,NC,R=301]
# END PHPBB PAGES
#####################################################

Robin_Bad:
доавьте в конец .htaccess:

RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^topic-t([0-9]+)\.html$ /topic$1\.html [R=301,L]

# TOPIC WITH VIRTUAL FOLDER ALL MODES
RewriteRule ^(forum|[a-z0-9_-]*-f)([0-9]+)/(topic|[a-z0-9_-]*-t)([0-9]+)(-([0-9]+))?\.html$ /viewtopic.php?f=$2&t=$4&start=$6 [QSA,L,NC]
# GLOBAL ANNOUNCES WITH VIRTUAL FOLDER ALL MODES
RewriteRule ^announces/(topic|[a-z0-9_-]*-t)([0-9]+)(-([0-9]+))?\.html$ /viewtopic.php?t=$2&start=$4 [QSA,L,NC]
# TOPIC WITHOUT FORUM ID & DELIM ALL MODES
RewriteRule ^([a-z0-9_-]*)/?(topic|[a-z0-9_-]*-t)([0-9]+)(-([0-9]+))?\.html$ /viewtopic.php?forum_uri=$1&t=$3&start=$5 [QSA,L,NC]

# TOPIC WITH VIRTUAL FOLDER ALL MODES
RewriteRule ^(forum|[a-z0-9_-]*-f)([0-9]+)/(topic|[a-z0-9_-])([0-9]+)(-([0-9]+))?\.html$ /viewtopic.php?f=$2&t=$4&start=$6 [QSA,L,NC]
# GLOBAL ANNOUNCES WITH VIRTUAL FOLDER ALL MODES
RewriteRule ^announces/(topic|[a-z0-9_-])([0-9]+)(-([0-9]+))?\.html$ /viewtopic.php?t=$2&start=$4 [QSA,L,NC]
# TOPIC WITHOUT FORUM ID & DELIM ALL MODES
RewriteRule ^([a-z0-9_-]*)/?(topic|[a-z0-9_-])([0-9]+)(-([0-9]+))?\.html$ /viewtopic.php?forum_uri=$1&t=$3&start=$5 [QSA,L,NC]