Before Rich Internet Application (RIA) comes to web application, we have to deal with the HTTP rule to handle flow within pages. My friend doesn’t know the problem why page control is so difficult. I think it is great to review those scenarios.

1. HTTP is stateless and synchronous. When user is adding stuff into shopping cart, you need to do session tracking. Because page and page needs to share user’s state.

Beginning HTTPSession from novice to professional.

2. When user submits the shopping form, and send to server, you need to know how to do with success, fail, or redirect from server. The user experience doesn’t have nervous to your response. Here is some useful tips.

Redirect After Post
GET after POST
How to redirect a web page, the smart way
Use standard redirects: don’t break the back button!
Redirect in response to POST transaction

3. When your pages have to keep server-side navigation history of visited Web pages and visited named sequences of Web pages, also known as Web flows. Web flows is more complicate, so I usually recommend to adapt framework.

Enable backwards navigation through Web applications
Spring Web Flow 2: A boon to JSF developers
Spring Web Flow for better workflow management in JSF
Spring Web Flow Examined

You may ask “Why should I know this?”, because those are the basic HTTP concept, and if you are interested, you can think more how they work in AJAX and RESTFul service. Enjoy!