The slides for the course are still hosted here, namely at http://www.cs.ru.nl/~erikpoll/websec/slides, as are some demo webpages thjat illustrate basic concepts such as JavaScript, the capabilities of the DOM that can be accessed via JavaScript, and the Same-Origin-Policy (SOP) to constraint interactions between content from different origins.
Does this webpage does pass the W3C Markup Validation Service? It should, really, but a few errors have been deliberately left to illustrate to complexity of HTML as a language.