[thelist] asp/c#/.net master page

[Lightening]

Hi- 
I am looking at:
http://www.codeproject.com/KB/aspnet/InsideMasterPages.aspx
in an effort to learn how to use master pages. 

There is a blurb of code I cannot reconcile. I am looking for help understanding it.

   //And finally on the content page, we add this snippet on the Load event.

   myMasterPage myMaster = (myMasterPage)this.Master;
   myMaster.mainTitle = "Playing with master pages :)";

The problem I am having with it is the writer doesn't tell us what he named his asst pages. 
I have a master page named MasterPage1.master. I have replaced different words 
in the above with "MasterPage1", but am not getting far. I am sure this is a 
silly-easy question, but, since this is a new area for me, I am lost.

Can someone here offer me how I should be wording this code?

thanks so much.
Laura