A cross-browser bookmarklet to examine the box-model of any DOM element on a page. Runs on Internet Explorer, Safari (and Webkit based browsers), Mozilla (including Firefox and Camino).
An online copy of O'Reilly's 2002 book Creating Applications with Mozilla. It focused on pre-1.0 versions of Mozilla, so details about the application structure has changed, but the XUL elements are relatively stable.
Dean Edwards counters Dojo's Alex Russell's hideous hacks with two standards friendly approaches. Looking at the The DOM Content loaded problem and the sluggishness of walking a DOM Tree, Dean talks about speed improvements, including the use of XPaths.