title: Why do we add dll in the web.config
body: <p>What is the advantage of add assembly in the <strong>web.config</strong></p>
  
  <pre><code>add assembly="System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/&gt;  
  </code></pre>
  
  <p>aganist adding assembly to the reference</p>
  
  <p>Any help is appreciated.
  TIA</p>