We have an application that we have 2 skins for reflecting the 2 customers of the application. When I went to using skins, I defeined the MasterPageFile in the web.config file rather than switching it programmatically in each page. Unfortunately, this meant that every time I wanted to view a page in Visual Studio 2005, I had to put the MasterPageFile statement back in the page - an extremely tedious problem. Since then, I have discovered that it is relatively easy to set the MasterPageFile in the Page_PreInit method which retains the statement in the aspx file making viewing in the designer still possible. I think this problem is sort of fixed in VS 2008 but switching it programmatically means one less thing that needs to be changed in the config file.