While Firefox 4.0 hasn't at the time of writing been officially released it is already on Mozilla public FTP servers.

The Mozilla Foundation, however, is cautioning people not to download the new browser from its sites yet, as the public copies now available are meant to be copied to mirror sites. A lot of traffic to these seed servers may slow propagation to more servers better equipped to handle a large amount of traffic.

This is not the first time that people have noticed that a new version of Firefox can be found online early. In fact, it is Mozilla's usual routine to post the browser first to the public FTP (File Transfer Protocol) so it can be copied to mirrors.

"C'mon Internet, we do this every time. We are seeding our FTP mirrors, but Firefox 4 isn't ready until www.mozilla.com/firefox says so!" said Mozilla's director of Firefox, Mike Beltzner, in a message posted on Twitter.

Those who truly cannot wait could also check with alternate file-sharing sites, such as FileForum, which has posted copies for Windows, Linux and Mac platforms.

More than nine months in development, Firefox 4 is a major upgrade to the open-source browser, featuring a revamped user interface, overhauled JavaScript engine, the ability to synchronize bookmarks across different copies of the browser and a wide range of other new features.

(Computerworld reporter Gregg Keizer contributed to this report.)