THE CODE DOCUMENTED HERE IS DEPRECATED. PLEASE SEE INSTEAD: JQuery HTML Updater
Your page needs to include the JS Prototype library. Currently, automatic inclusion of the Prototype library isn't working, so you'll need to include a <script> line to do so. You can link to the prototype library in Umlaut, see example below.
Umlaut base URL
The first argument is your Umlaut base URL. This is not your link resolver base url which for Umlaut ends in /resolve, but the actual Umlaut application base URL, which should be the same, without the /resolve. (Link to JHU example removed, because i think it was attracting malicious bot/spider traffic)
The second argument is a URL-formatted (KEV) OpenURL context object.
Display section mappings
The fourth argument is a hash of additional options to embedUmlaut.
The html loaded will sometimes include a "spinner" with a message "loading more", if the content is not yet loaded.
An example is best: