I get this massge from the my VPS server that i instell my script (web)

Internal Server Error

The server encountered an internal error or misconfiguration and was unable to complete your request.

Please contact the server administrator at webmaster@domain.com to inform them of the time this error occurred, and the actions you performed just before this error.

More information about this error may be available in the server error log.

Additionally, a 500 Internal Server Error error was encountered while trying to use an ErrorDocument to handle the request.

Apache/2 Server at www.domain.com Port 80
i know that my .htaccess is the Problem or my mod_rewrite is not working?

this is my .htaccess:
RewriteEngine on

Options -Indexes

ErrorDocument 404 http://www.domain.com/index.html
ErrorDocument 403 http://www.domain.com/index.html

RewriteRule ^,(.*)$ modules.php?mod=$1 [L]

RewriteRule ^index.html$ index.php [L]

RewriteRule ^rss.xml$ rss.php [L]

RewriteRule ^rss.xml?(.*)$ rss.php?$1 [L]

RewriteRule ^rss.html$ modules.php?mod=downloads,rss [L]

RewriteRule ^submit.html$ modules.php?mod=downloads,submit [L]

RewriteRule ^chat.html?(.*)$ ,downloads,chat?$1 [L]

RewriteRule ^contact.html$ modules.php?mod=contact [L]

RewriteRule ^download_([0-9]*)(.*)$ modules.php?mod=downloads,$1 [L]

RewriteRule ^cat_([0-9]*)(.*)$ modules.php?mod=downloads,cat_$1 [L]

RewriteRule ^page_([0-9]*)(.*)$ modules.php?mod=pages,_$1 [L]

RewriteCond %{HTTP_HOST} ^iwarez\.tv
RewriteRule ^(.*)$ http://www.domain.com/$1 [R=permanent,L] 

RewriteCond %{HTTP_HOST} ^domain\.
RewriteRule ^(.*)$ http://www.domain.com/$1 [R=permanent,L] 

RewriteCond %{HTTP_HOST} ^www\.domain\.com
RewriteRule ^(.*)$ http://www.domain.com/$1 [R=permanent,L] 

AuthGroupFile /dev/null

AuthName "domain.com"

AuthType Basic

AuthUserFile /home/admin/domains/domain.com/.htpasswd/public_html/.htpasswd
way the site is not working? thank you for the help!