As an ASP.NET web developer, I think it's important to understand and know how to configure Microsoft's web server, Internet Information Services (IIS). Depending on the organisation you work for you may or may not get the opportunity to tinker with IIS, but this shouldn't stop you from learning the basics. You could go out and buy a book on configuring IIS and then install IIS on your computer to practise what you've read, but thanks to the guys at Trainsignal.com who have kindly sent me some of their training videos, I've discovered a much easier way of learning.