AJAX / CSS - AHAH: Asychronous HTML and HTTP

AHAH is a very simple technique for dynamically updating web pages using JavaScript. It involves using XMLHTTPRequest to retrieve (X)HTML fragments which are then inserted directly into the web page, whence they can be styled using CSS.
AHAH is intended to be a much simpler way to do web development than AJAX. Strictly speaking, AHAH can be considered a subset of AJAX, since (X)HTML is just a special kind of XML.
http://microformats.org/wiki/rest/ahah