Introduction

You surely know how typical web applications work. You enter a URL in your browser and the browser loads that page for you. If you are required to submit a form, you will fill it and the browser sends the filled data to the server side for processing. During this time you wait for the entire page to load. If you are on a slow connection, the wait is even longer.

Let me describe another typical scenario, a web page has two select boxes. The first select box asks you to select the name of a country. You make your selection and the whole page loads to populate the second select box with the names of the cities in that country. If by mistake you made a wrong selection, fixing your mistake means another page load. Irritating isn't it?

The point I am trying to make here is: why load the complete page every time? Why can't you just select the country name and using some magic in the background be provided with the city list without loading the complete page? Maybe you can fill some other...