Answered "503 Error" for invalid subdomain URL instead site start redirection

Rewrite Base /subdir/

mydomain.com/subdir/

# The Friendly URLs part
# detect language when requesting the root (/)
RewriteCond %{HTTP:Accept-Language} !^de [NC]
RewriteRule ^$ en/ [R=301,L]
RewriteRule ^$ de/ [R=301,L]
 
# redirect all requests to /en/favicon.ico and /de/favicon.ico
# to /favicon.ico
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^(en|de)/favicon.ico$ favicon.ico [L,QSA]
 
# redirect all requests to /en/assets* and /de/assets* to /assets*
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^(en|de)/assets(.*)$ assets$2 [L,QSA]
 
# redirect all other requests to /en/* and /de/*
# to index.php and set the cultureKey parameter
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(en|de)?/?(.*)$ index.php?cultureKey=$1&q=$2 [L,QSA]
- See more at: http://www.multilingual-modx.com/blog/2011/seo-friendly-multilingual-websites-with-modx-and-babel.html#sthash.PJie4Zdt.dpuf