JavaScript has been a feature of browsers since way back in 1995. Often derided as a "toy" language, JavaScript used to be seen as an optional extra -- where turning it off would have no great detrimental effect on the workings of a site.

How times have changed.

Now, after the AJAX revolution, JavaScript is not only vital to the proper functioning of web pages, but the performance of the JavaScript engine is vital.

I'll give you a simple example. Try using the new Google Sites using IE6 and then try again using the Firefox 3 release candidate. The difference is simply astounding.

IE 6 is very sluggish, and actually will often time out while trying to load pages, particularly if you're using tables of any size. Go and get a cup and coffee while loading the "Edit" screen.

By comparison, FF3 is lightning fast -- far faster than even previous generations of FF or the Mozilla Suite products. I haven't tested performance against Safari or other WebKit browsers, but it's clear a new front has just opened in the browser war: the speed of your JavaScript interpreter.

May the best man win!