title: Missing "System.web" reference in ASP.NET
body: <p>Within my project I have gotten this error:</p>
  
  <blockquote>
    <p>Error 1  The type or namespace name 'UI' does not exist in the namespace 'System.Web' (are you missing an assembly reference?)    </p>
  </blockquote>
  
  <p>So, basically I attempted to add "system.web" as a reference to my project, but there is no such thing exist in my <a href="http://en.wikipedia.org/wiki/.NET_Framework" rel="nofollow">.NET</a> framework.</p>
  
  <p>How can I install "system.web"?</p>