Earlier web applications were limited because a web page had to be reloaded to obtain a data.
HTML and CSS
XML and XSLT
Ajax allows displaying web pages with interactive, efficient and quick interfaces, the benefits behind Ajax have pushed several web developers to program websites by implementing Ajax, web giants like Google, effectively utilize Ajax in their web applications like Gmail and Google Maps.
Fast buffering of data
The most important feature of AJAX which makes it more popular among the people is that it is open source application developer software. This means anybody can modify the code of AJAX to implement more features and can assimilate that updated version to be used by all for completely free of cost.