We will start introducing Ajax into our application by implementing live searching. The idea behind this feature is simple: when the user types a few keywords into a text field and clicks search, a script works behind the scenes to fetch search results and present them on the same page. The search page does not reload, thus saving bandwidth, and providing a better and more responsive user experience.
Before we start implementing this, we need to keep in mind an important rule while working with Ajax: write your application so that it works without Ajax, and then introduce Ajax to it. If you do so, you ensure that everyone will be able to use your application, including users who don't have JavaScript enabled and those who use browsers without Ajax support.