RewriteEngine On

RewriteCond %{REQUEST_METHOD} ^TRACE

RewriteRule .* - [F]

RewriteRule ^([0-9]+)$ info.php?nk=$1 [L,QSA]

RewriteRule ^id([0-9]+)$ info.php?nk=$1 [L,QSA]

RewriteCond %{HTTP_HOST} ^([a-z1-9_-].{3,})\.site.ru$ [NC]

RewriteRule ^$ http://site.ru/? [R=301,L]

RewriteRule ^id([0-9]+)$ info.php?u=$1 [L]

RewriteCond %{HTTP_HOST} ^([a-z1-9_-]+)\.site\.ru$ [NC]

RewriteCond %{HTTP_HOST} !^www\.site\.ru$ [NC]

RewriteRule ^(.*)$ http://site.ru/info.php?u=%1 [R,QSA]