Redirect Using .htaccess

RewriteEngine On

rewritecond %{http_host} ^mydomain.com [nc]
rewriterule ^(.*)$ http://www.mydomain.com/$1 [r=301,nc]


RewriteCond %{THE_REQUEST} ^[A-Z]{3,9}\ /index\.php\ HTTP/
RewriteRule ^index\.php$ http://www.mydomain.com/ [R=301,L]


ErrorDocument 404 http://www.mydomain.com/404.htm