I mean, I understand the difference between showing actual actions or giving more space to content, but I'd like to know of some real studies on it.
demo: http://terkel.jp/demo/jquery-floating-widget-plugin.html
This sniffing in particular will fail for Opera 6-8, therefore excluding perfectly capable browsers by a very shallow criterion.
The sniff serves no purpose, and is furthermore based upon a thoroughly disproved anti-pattern.
Edit: The sidebar containing (Intro, HTML, CSS, Javascript, Download, MOJO) "sticks" to the page as your scroll down