Redirect IE7 or below users to a new page
I agree with Bryan, personally I like to use the Browser-Update.org notification.

Nevertheless, if you want to use .htaccess just make sure you put your redirect code before Crafts routing:

&lt;IfModule mod_rewrite.c&gt;
    RewriteEngine On

    # Redirect old Browsers
    RewriteCond %{HTTP_USER_AGENT} "MSIE [1-7]" [NC]
    RewriteRule ^(.*)$ http://something.com/else [R=301,L]

    # Crafts routing
    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteCond %{REQUEST_URI} !^/(favicon\.ico|apple-touch-icon.*\.png)$ [NC]
    RewriteRule (.+) index.php?p=$1 [QSA,L]
&lt;/IfModule&gt;