You can use Rewrite in .htaccess to do that. Test for the particular browser (user-agent as it is called in htaccess language) and then send the surfer somewhere else. It would go something like this (showing 2 test conditions, just add [OR] to each line except the final test if you want to include a bunch of browsers):

RewriteEngine on
RewriteCond %{HTTP_USER_AGENT} ^Opera [OR]
RewriteCond %{HTTP_USER_AGENT} ^SomeOtherBrowser
RewriteRule ^(.*)$ http://www.someothersite.com/

However, it's more common to let the user enter and then test in PHP/HTML/CSS to see which browser it is and selectively use bits of code to ensure the page displays well with that particular browser. It's normally much easier to include a bit of extra conditional code in a single page than to maintain duplicate pages/sites for various browsers.

Kevin