But here outside Brightspace you can also access the slides and the demo webpages. The demo webpages illustrate concepts such as JavaScript, the DOM API that can be accessed via JavaScript, and the Same-Origin-Policy (SOP) to constraint interactions between content from different origins.
This webpage does not meet the W3C guidelines for valid HTML, as you can check using the W3C Markup Validation Service but that is done on purpose to illustrate to horrendous complexity of the HTML standard, which is updated on a weekly (!) basis.