There is an article on MSDN about how to get round the ActiveX activation issues that will be introduced into IE shortly. On that page it mentioned something I didn’t know - the latest version of Netscape Browser (version 8) can use Internet Explorer’s rendering engine (Trident) instead of the Mozilla rendering engine, Gecko.
If you develop web sites these days you need to make sure you can support at least IE and Firefox and preferably Safari. Testing Safari is often not possible if you primarily use Windows but testing in IE and Firefox can now be done from the same browser - you can actually change rendering engine at any time with CTRL-SHIFT-E. It also supports all the cool developer features of Firefox (like the DOM Inspector (although if you are using the IE rendering engine you can’t just click an element to select it).