Safari 5 is my new favorite browser, but I was a little hesitant to upgrade until I’d figured out how I could keep Safari 4. The Multi-Safari project solves that handily.
The Multi-Safari website allows you to download all the previous versions of Safari back to 1.0. Every version is specially packaged to use the WebKit rendering engine that was available at the time of release.
Now, in my Applications folder, I have Safari 2.0.app, Safari 3.2.1.app, Safari 4.0.5.app and Safari.app (Safari 5), along with the WebKit Nightly. (While running Mac OS X 10.6 Snow Leopard, the oldest version I’m able to run is Safari 2.0.)
Although Safari does not have the market fragmentation of IE, it can be useful to have older versions around for testing Ext JS. Plus, I’m just kinda sentimental like that.