Configuration Error in asp.net
<p>i developing a application. when i run the application in my system it is giving this error please could you help me.</p>

<blockquote>
  <p>Description: An error occurred during
  the processing of a configuration file
  required to service this request.
  Please review the specific error
  details below and modify your
  configuration file appropriately.</p>
  
  <p>Parser Error Message: Could not load
  file or assembly
  'System.Web.Extensions,
  Version=1.0.61025.0, Culture=neutral,
  PublicKeyToken=31bf3856ad364e35' or
  one of its dependencies. The system
  cannot find the file specified.</p>
</blockquote>

<p>Source Error: </p>

<pre><code>Line 33:        &lt;compilation debug="true"&gt;
Line 34:            &lt;assemblies&gt;
Line 35:                &lt;add assembly="System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"/&gt;
Line 36:                &lt;add assembly="System.Design, Version=2.0.0.0, Culture=neutral, PublicKeyToken=B03F5F7F11D50A3A"/&gt;
Line 37:                &lt;add assembly ...
</code></pre>
