Yes, what is that…? Yes, you canot do anything bit with it. But if you really think about the user experience in ASP.NET AJAX UI, then better to consider about this property.

As you know some ASP.NET AJAX application’s UI loads bit fast but it takes few seconds to interact with user. In other hand some application’s UI takes more times to load, but user can interact with UI as soon as it loads. So, simply you can choose the option with ASP.NET AJAX ScriptManager like below…

If you set ScriptManager.LoadScriptsBeforeUI = True, then script load first and next UI markup. If you set ScriptManager.LoadScriptsBeforeUI=False, then UI load first and next Script. So, UI will load some fast but have to wait till script load.

FYI: LoadScriptsBeforeUI default value is TRUE.