Did you know that spoofing your useragent is not enough for protecting the identity of your browser? Web developers can also rely upon the navigator object to identify your browser. To properly protect your browser identity, you also need to spoof your navigator object. I find it stupid how some web developers refuse to show websites to browsers other than Firefox - you're not supposed to rely upon the useragent OR navigator data.
PHP's $_SERVER['HTTP_USER_AGENT'] variable: