Difference between the Web.config of a ASP.Net Website and an ASP.NET AJAX Enabled Website

When you create a new AJAX-enabled Web site, you can use the Web.config file provided in the installation package to add the required configuration settings. In Visual Studio, the Web.config file for Microsoft ASP.NET AJAX is included in your project when you create a new ASP.NET AJAX-enabled Web Site. But in a Normal ASP.Net Ajax website, you need to add it manually by right clicking on the Website in the Solution explorer.

Adding ASP.NET AJAX Configuration Elements to an Existing Web Site
In an existing Web site, you typically have values in the Web.config file that you want to retain. In that case, you can add the new ASP.NET AJAX elements into the existing Web.config file.
The new elements are part of the following configuration sections:
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