<IfModule mod_rewrite.c>
Options +FollowSymLinks
RewriteEngine On
RewriteBase /
# HTTPS
RewriteCond %{ENV:HTTPS} !on
RewriteCond %{REQUEST_URI} !robots.txt
RewriteRule ^(.*)$ https://%{HTTP_HOST}%{REQUEST_URI} [R=301,L]
# /
#RewriteCond %{REQUEST_FILENAME} !-f
#RewriteCond %{REQUEST_URI} !(.*)/$
#RewriteRule ^(.*)$ /$1/ [R=301,L]
# a
RewriteRule ^a/$ /c/a/auth/index.php [QSA,L]
# b
RewriteRule ^b/(.*)/$ /b/?q=$1 [QSA,L]
# c
RewriteRule ^(.*)/$ ?q=$1 [QSA,L]
</IfModule>
з.ы. И статья про mod_rewrite то что нужно - вникаю