There are hundreds of articles on the net for Master Pages. Most of them just have screen shots pasted into them telling you how to a create a Master and Child page.
I have just filtered the links on the internet for you. These articles describe in detail how master pages work and how to tweak them :
- ASP.Net 2.0 – Master Pages: Tips, Tricks, and Traps -http://www.odetocode.com/Articles/450.aspx
- Introducing ASP.NET 2.0 Master Pages – http://www.devx.com/dotnet/Article/18042
- A Sneak Peak at MasterPages in ASP.NET 2.0 –http://aspnet.4guysfromrolla.com/articles/010505-1.aspx
- Master Pages in ASP.Net 2.0 – An Advanced Look –http://www.beansoftware.com/ASP.NET-Tutorials/Master-Pages.aspx
- Dynamically Loading Master Pages in ASP.NET 2.0 (BLOG Post) – http://ryanfarley.com/blog/archive/2004/06/16/788.aspx