How can you detect the version of a browser?

Question

I\'ve been searching around for code that would let me detect if the user visiting the website has Firefox 3 or 4. All I have found is code to detect the type of browser but

Answer 1

The bowser JavaScript library offers this functionality.

if (bowser.msie && bowser.version <= 6) {
  alert('Hello China');
}

It seems to be well maintained.