Visual Studio Community 2015 schema error in web.config

We migrated a ASP.Net 2.0 - C# website from a Windows Server 2003 environment to a Windows Server 2012 environment.    The website appears to run fine however when using Visual Studio Community 2012 the site web.config file is calling out virtually all <add name=  and < add assembly=  statement with the error message"

Could not find schema information for the attribute 'assembly'.