GMW/packages/AjaxControlToolkit.7.1213/content/web.config.transform

<?xml version="1.0"?>
<configuration>
  <system.web>
    <pages>
      <controls>
        <add tagPrefix="ajaxToolkit" assembly="AjaxControlToolkit" namespace="AjaxControlToolkit" />
      </controls>
    </pages>
  </system.web>
</configuration>