Ajax allows web pages to be updated asynchronously by exchanging data with a web server behind the scenes, allowing web page updates without reloading the entire page. It uses a combination of technologies including XHTML, CSS, DOM, XML, XSLT, XMLHttpRequest, and JavaScript. Some of the major companies using Ajax include Google with applications like Google Maps, Gmail, and Google Groups, as well as Flickr, A9.com, and Meebo. Ajax frameworks help developers implement Ajax and include Dojo, RIALTO, ASP.NET AJAX, Google Web Toolkit, and Script.aculo.us.