What is XmlHttpRequest in Ajax?

It is an object in Javascript that allows the browser to communicate to a web server asynchronously without making a postback.

What is Ajax?

Asyncronous Javascript and XML – Ajax is a combination of client side technologies that sets up asynchronous communication between the user interface and the web server so that partial page rendering occur instead of complete page postbacks.

Is it possible to debug java-script in .NET IDE? If yes, how?

Yes, simply write “debugger” statement at the point where the breakpoint needs to be set within the JavaScript code and also enable JavaScript debugging in the browser property settings

What is the difference between Server-side scripting and Client-side scripting?

Server side scripting :
means that all the script will be executed by the server and interpreted as needed. ASP doesn’t have some of the functionality like sockets, uploading, etc.
Client side scripting :
means that the script will be executed immediately in the browser such as form field validation, clock, email validation, etc. Client side scripting is usually done in VBScript or JavaScript.

What is Ajax? What is ASP.NET AJAX?

The term Ajax was coined by Jesse James Garrett and is a short form for “Asynchronous Javascript and XML”. Ajax represents a set of commonly used techniques, like HTML/XHTML, CSS, Document Object Model(DOM), XML/XSLT, Javascript and the XMLHttpRequest object, to create RIA’s (Rich Internet Applications).
Ajax gives the user, the ability to dynamically and asynchronously interact with a web server, without using a plug-in or without compromising on the user’s ability to interact with the page. This is possible due to an object found in browsers called the XMLHttpRequest object.

ASP.NET AJAX :-

‘ASP.NET AJAX’ is a terminology coined by Microsoft for ‘their’ implementation of AJAX, which is a set of extensions to ASP.NET. These components allow you to build rich AJAX enabled web applications, which consists of both server side and client side libraries.
Which is the current version of ASP.NET AJAX Control Toolkit?
As of this writing, the toolkit version is Version 1.0.20229 (if you (if you are targeting Framework 2.0, ASP.NET AJAX 1.0 and Visual Studio 2005) and Version 3.0.20229 (if targeting .NET Framework 3.5 and Visual Studio 2008).

How can we call javascript function in page load event?

this.button.Attributes.Add("OnClick",return functionname(););

Which is the method to register javascript in ASP.NET?

Client.RegisterStartupScript()

Eg: ClientScript.RegisterStartupScript(GetType(), "key", "script");