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).
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.