Required Capabilities

Exactly what are the capabilities required of a browser to run AJAX functionalities? As mentioned,
a browser needs to provide two key capabilities: a proxy mechanism to make client
code able to place out-of-band HTTP calls, and an updatable DOM.

There’s a W3C ratified standard for the updatable DOM. A W3C standard for the proxy component
is currently being developed. It takes the form of the XMLHttpRequest object and is
devised as an interface exposed by the browser to allow script code to perform HTTP client
functionality, such as submitting form data or loading data from a remote Web site. The latest
working draft is available at http://www.w3.org/TR/XMLHttpRequest.

In addition, browsers must support JavaScript and preferably cascading style sheets (CSS).
In the end, the AJAX lifestyle is possible and affordable for virtually every developer and nearly
90 percent of the Web audience, regardless of the platform. The tools required to make AJAX
work are becoming as ubiquitous as HTML/XML parsers, HTTP listeners, and JavaScript
processors. To paraphrase the catch phrase of a popular advertising campaign, I’d say that
“AJAX is now.” And as far as the Windows and ASP.NET platforms are concerned, AJAX takes
the form of Microsoft ASP.NET AJAX Extensions.