WSSv3/Sharepoint 2007 does not support nested master pages
For a Project I had on a SharePoint site I thought it would be a good idea to create a new master page that is based on the default.master and exposes some placeholder for my content pages to use. Nested Master Pages are trivial to do in ASP.net normally, but for some reason on my SharePoint site, the child page was not rendering its content in one of the new placeholders.
Well, turns out that SharePoint 2007/WSSv3 explicitly does not support nested master pages. To quote an Article in MSDN directly:
Although the underlying technology enables the creation of nested master pages, nested master pages are not supported in Windows SharePoint Services. Using nested master pages can cause unexpected behavior in some scenarios, such as preventing content from rendering.
Indeed, unexpected behavior, such as content not rendering is the exact problem I have. Now I remember why I love SharePoint so much: It's taking the essential functions of ASP.net and then adds some traps that really hurt you unexpectedly.