Recently I was updating some ASP.NET pages for a client. They had a set of custom-built server controls that worked very happily, binding data to and from domain objects. I modified some of the ASP.NET pages so that they became Content pages that shared a common Master page. Then suddenly all the Server controls stopped working - they were not processing postbacks properly or firing events. That is, Server Controls that had worked in normal ASP.NET pages suddenly stopped working in Master-Content pages.