I think I've found a bug (Broken link, was originally lab.msdn.microsoft.com/productfeedback/viewfeedback.aspx?feedbackid=f0a9000e-3ce5-46c2-b10f-343b8126a0c7) in ASP.NET Master Pages - if you try to include any <%= %> tags in a ContentPlaceHolder control on a Master Page, then it doesn't get overidden by the content in the Content control.