The .htaccess file contains the main rules for request routing. The recommended content is:
Options +FollowSymLinks +ExecCGI
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteCond %{REQUEST_URI} !/images
RewriteRule ^(.*\.(jpg|gif|png))$ /images/$1 [L,PT]
RewriteCond %{REQUEST_URI} !/layout
RewriteRule ^(.*\.(css))$ /layout/$1 [L,PT]
RewriteCond %{REQUEST_URI} \..+$
RewriteCond %{REQUEST_URI} !\.html$
RewriteCond %{REQUEST_FILENAME} -f
RewriteRule .* - [L]
RewriteRule ^(.*)$ index.php [QSA,L]
</IfModule>