Testing various flavors of Internet Explorer is much easier now thanks to smart & giving coders. The following instructions will allow you to install IE6/7/8/9 in different virtual machines so you can test each version of IE. This is much better than BootCamp since (a) you can run this directly in Max OS X (no need for restarts) and (b) you can have multiple versions of browsers.
1 – Follow installation instructions here: https://github.com/xdissent/ievms/
2 – Start VirtualBox and pick your virtual machine / version of IE to use
3 – Your host machine IP address is by default 10.0.2.2. So for example, if you’re running a rails app on your mac, you can connect to it in Internet Explorer via http://10.0.2.2:3000.
The installation process if pretty long, but once its up and running its cake to get to debug on a particular version of IE.