Can we run ASP.NET 1.1 application and ASP.NET 2.0 application on the same computer?

Yes, though changes in the IIS in the properties for the site have to be made during deployment of each.

Explain the concept of Web Application.

An introduction to web applications
A web application consists of a set of web pages that are generated in response to user requests. The Internet has many different types of web applications, such as search engines, online stores, auctions, news sites, discussion groups, games, and so on.

Properties of web applications

Web applications are a type of client/server application. In that type of application, a user at a client computer accesses an application at a server computer. In a web application, the client and server computers are connected via the Internet or via an intranet (a local area network).
In a web application, the user works with a web browser at the client computer. The web browser provides the user interface for the application. The most popular web browsers are Microsofts Internet Explorer, .Mozilla Firefox
The application runs on the server computer under the control of web server software. For ASP.NET web applications, the server must run Microsofts web server, called Internet Information Services, or IIS.

For most web applications, the server computer also runs a database management system, or DBMS, such as Microsofts SQL Server. The DBMS provides access to information stored in a database. To improve performance on larger applications, the DBMS can be run on a separate server computer.

The user interface for a web application is implemented as a series of web pages that are displayed in the web browser. Each web page is defined by a web form using HTML, or Hypertext Markup Language, which is a standardized set of markup tags.
The web browser and web server exchange information using HTTP (Hypertext Transfer Protocol).

Which Javascript file is referenced for validating the validators at the client side?

WebUIValidation.js Javascript file installed at “aspnet_client” roots IIS directory is used to validate the validation controls at the client side.

What is Internet Information Services, and what’s it used for?

Internet Information Services (IIS) is a Web server used to run Internet applications.

What is the difference between Server-side and client-side code?

Server side code is executed at the server side on IIS in Asp.NET framework, while client side code is executed on the browser.

What is the main disadvantage of using IIS to host a service?

Using IIS to host your services means that you will not be able to support non-HTTP protocols such as TCP, named pipes, and MSMQ. You will have access to the many built-in features available with IIS such as process recycling and message based activation.

Is IIS require to run asp.net Web applications?

If you are using Visual Studio, you can use the ASP.NET Development Server built into Visual Studio to test your pages. The server functions as a local Web server, running ASP.NET Web pages in a manner virtually identical to how they run in IIS. To deploy a Web application, you need to copy it to a computer running IIS version 5 or 6.