# вывод отдельному тегу
RewriteRule ^tags/([^/]*)(/?)+$ index.php?do=tags&tag=$1 [L]
RewriteRule ^tags/([^/]*)/page/([0-9]+)(/?)+$ index.php?do=tags&tag=$1&cstart=$2 [L]

RewriteRule ^tags(/?)+$ index.php?do=alltags
RewriteRule ^tags/page/([0-9]+)(/?)+$ index.php?cstart=$1&do=alltags