IWML (IntraWeb Markup Language) is a component based representation used to communicate between web browser and web server. IWML is platform independent and not bound to HTML.
IWML can be generated dynamically from a server, or static .iwml files can be used. IWML is fully expandable with provisions for custom components and loadable extensions.
IWML is a sub type of the ACORN format.
If you are new to IWML, consider following the IWML tutorial.