I've been noticing some warnings with various config files that Visual Studio creates/maintains/updates and I thought I'd have a closer look. In particular, warnings regarding the section.requirePermission attribute and the trace/listeners/add.initializeData attribute.
When I first looked at these config files there was no xmlns attribute on the configuration element, so, I thought that was the cause. A little research seemed to show that xmlns="http://schemas.microsoft.com/.NetConfiguration/v2.0" was the configuration file namespace. Adding the xmlns attribute to the configuration section quickly made Visual Studio not recognize any elements--clearly the wrong thing to do.
I then had a look at properties for the app.config document in Visual Studio and it showed "C:\Program Files\Microsoft Visual Studio 8\xml\Schemas\DotNetConfig.xsd" in the Schemas property. Once I had a look at this DotNetConfig.xsd file I found what the problem was. This file is not completely accurate when compared to the documented attributes; in particular it didn't have schema information for the two aforementioned attributes.
So, I quickly added the schema information and the warnings disappeared.
This is the results of that research. See http://www.peterritchie.com/Hamlet/Articles/75.aspx to discuss this.