Browser language redirection

Hi there. I have a multilingual wordpress blog and I would like to have my guest be redirected (on server-side) to pages that reflect their language.

I use qTranslate plugin that transform URLs in that way:

site.com <— preferred language
site.com/fr/ <— french page
site.com/it/ <— italian page

and so on. I’ve searched for a lot of time a way to accomplish this but without fortune. I can’t find appropriate plugin nor other techniques that work well. Did you know how to do this?

I’ve tried to change my .htaccess:

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteCond %{HTTP:Accept-Language} ^.*(it).*$ [NC]
RewriteRule ^(index\.php)$ http://www.my-site.com/it/ [L,R=301]
</IfModule>

or

RewriteCond %{HTTP:Accept-Language} !en [NC]
RewriteCond %{HTTP:Accept-Language} it [NC]
RewriteRule .* http://www.my-site.com/it/ [R,L]

but nothing.

Thanks in advance