In the previous chapter, we introduced Ajax, a collection of web techniques to update parts of the screen in web applications without having to create a link to a physically different page, have the browser request that new page from the server, and load it. Modern websites use this technique all over the place, as do their developers; Ajax is a common practice, a commodity almost.

The concept is, however, difficult to grasp by both the marketing people you have to work with and the visitors of your site. Doesn't it often occur that your marketing person asks you to add a page to the website and then wants to know what the URL is? It is index.php, honey, it always is. Visitors of your site who navigate through the menus will, when they hit the browser's back button, expect to look at the screen they just left. Instead they will be taken back to the website they were visiting before coming to yours, unless you use the techniques we are...