.NET allows you to call a JavaScript function from the server-side code. For example, suppose you want to to display a message box to the user. This can be accomplished in two steps:

1. Write a JavaScript function in the HTML view of the page inside the &ltHEAD&gt elements as shown below:

2. In the code behind file of the .aspx page, add the following line of code in the page load function:

        private void Page_Load(object sender, System.EventArgs e)     {        Button1.Attributes.Add("OnClick", "ShowAlert();");     }

Now, compile the project and run it. Clicking the button on the page, you can see the message box displayed.