As a web developer, you probably know all about browsers. They suck. Well, some more than others. But, if you develop apps for Windows users, you’ll have to test your app with Internet Explorer.
Now, as a good Rails developer, I’m using a Mac. I can test apps with FireFox, Safari and Opera without problems. But Internet Explorer is always a problem. I used Parallels for a while to run an instance of Windows XP to test with IE.