Modern software releases patches and updates incrementally, meaning you only have to download the code that is different. This allows for much smaller and more effective downloads. Patching systems such as this have been around since software had version numbers. Why then does Firefox require you to download the full program every time a new version is released? Updating from v1.0.2 to v1.0.3 requires a 4MB download for a meager .01 version update. Don't get me wrong the security updates are welcome and show that the developers are committed to their product. It is the way that they are released I question.

The Firefox Update Conspiracy