Date: 11/30/05 (Java Web)    Keywords: xml, web

As you probably know XmlHttpRequest only works if the request is made to the same web server from which the page was fetched (same origin). Here is a way to communicate across sub-domains using XmlHttpRequest without resorting to reverse proxying. Abe (@ fettig.net) found a solution using iframe and an exception to the "same origin" rule. [...]

Source: http://blog.taragana.com/index.php/archive/xmlhttprequest-across-sub-domains/