.htaccess

RewriteEngine On
RewriteBase /

RewriteCond %{REQUEST_URI} \.xhtml$
RewriteCond %{HTTP_USER_AGENT} MSIE [OR]
RewriteCond %{HTTP_ACCEPT} application/xhtml\+xml\s*;\s*q=0\.?0*(\s|,|$)
RewriteRule .* - [T=text/html]

RewriteCond %{QUERY_STRING} lang=(en|fr|de)
RewriteRule .* $0? [CO=lang:%1:%{HTTP_HOST},R,L]

RewriteCond %{HTTP_COOKIE} lang=(de|fr|en)
RewriteRule .* %1/$0 [L]

RewriteCond %{HTTP:Accept-Language} ^(en|fr|de).*$
RewriteRule .* %1/$0 [L]

RewriteRule .* fr/$0 [L]

ExpiresActive On
ExpiresDefault "access plus 0 seconds"