Web 2.0 (Ajax)
Every piece of data transmitted between client and server is optimized, and no data are transmitted twice. In other words, using such application is much faster than using standard Web 1.0 applications.
A standard Web 1.0 application reloads the entire web page after each click (including menus, header and footer), while a Web 2.0 application loads the design of web page in one request and later only clean data is transmitted.
There are several more advantages to use Web 2.0 application: Since the browser communicates with a server using API, you can use the same API from your custom application and automate some of the actions of a third party software.