RewriteEngine on

RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^category([0-9a-zA-Z_\-]+).html$ ?category=$1 [L]
RewriteRule ^special([0-9a-zA-Z_\-]+).html$ ?special=$1 [L]
RewriteRule ^([0-9a-zA-Z_\-]+).html$ ?article_id=$1 [L]