Script combining is the process of merging multiple scripts into one script so that it can be downloaded with a single network call. By using script combining, frequently used scripts or script dependencies can be combined, placed on the server, and then downloaded using the Script Loader. The ASP.NET Ajax Library provides support for loading combined scripts defined in Start.js or in custom metadata scripts. This HOW TO tutorial will demonstrate how script combining works and how you can take advantage of it in your Ajax applications. The ASP.NET Ajax Library's Start.js file defines several different scripts and their dependencies. An example of the definition for the MicrosoftAjaxCore.js and MicrosoftAjax.js files Read more: ASP.NET Ajax