RewriteEngine On
RewriteBase   /_dev
RewriteRule ^$ /_dev/ [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_URI} !^/_dev/
RewriteRule ^(.*)$ /_dev/$1
RewriteCond %{SCRIPT_FILENAME} -d
#RewriteRule ^_dev/(.*[^/])$ http://localhost/$1/ [R=301]