title: Reference issues in .NET 4.0 project to .NET 2.0 dll/project
body: <p>I just starting to use Visual Studio 2010 and .NET 4.0.  I created a new WPF project a DLL built for .NET 2.0.  When I build the project, I get a bunch of warnings like this one:</p>
  
  <pre><code>The referenced assembly
  "MicroFour StrataFrame Business...processorArchitecture=MSIL"
  could not be resolved because it has a dependency on
  "System.Web, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a"
  which is not in the currently targeted framework ".NETFramework,Version=v4.0,Profile=Client".
  Please remove references to assemblies not in the targeted framework
  or consider retargeting your project.
  </code></pre>
  
  <p>When I reference a project I created that targets 3.5, it can't find any of the namespaces (during compile), though they show up in the object browser and intellisense correctly shows them.</p>
  
  <p>Is there something I'm missing that needs to be done to reference an older .NET assembly?</p>