The content you're reading has been loaded asynchronously in the background and inserted into a <DIV> in the document. You can use this script to make any element behave as a container, loading partial HTML content and the output of GET and POST form requests unmodified, without any script in the loaded files!
This script is therefore ideal for dynamically updating areas of your page via script control or user initiation, and constructing rich client-side web applications that send and retrieve data to/from a server.
It wraps up the 'XMLHttpRequest' object supported by many modern browsers in a handy API supporting multithreaded document loading and form posting. Additionally, it includes an additional custom-written hidden-IFRAME-based transport layer that adds broader browser support, including IE4+ on Windows, IE5+ on Mac, Opera 7.0 and higher, Safari, Mozilla, and more. XMLHttpRequest by itself supports only IE5+/Windows, Mozilla, Safari 1.2+, and Opera 8.0+.