web.config error: Could not find schema information for the element 'case'.

I've added the section below trying to have my menu displayed correctly in the Chrome browser.

However, VS2008 complains:

Message 1 Could not find schema information for the element 'case'.

Message 2 Could not find schema information for the attribute 'match'.

The assemblies listed below are present but clearly one or more is missing. Which please?

/gustav

 

From web.config: 

<add assembly="System.Core, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>

<add assembly="System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/>

<add assembly="System.Data.DataSetExtensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>

<add assembly="System.Xml.Linq, Version=3.5.0.0, Culture=neutral, PublicKeyToken=B77A5C561934E089"/>

< ...