I was revisiting some old scripts I had written for determining the size of the browser window (or things inside it) -- using clientWidth for IE and innerWidth for Netscape / other. Like many scripts written for the good old days, measuring seems to have changed as well.
Mark Wilton-Jones provides this rather frightening analysis http://www.howtocreate.co.uk/tutorials/javascript/browserwindow of the behavior of Opera, IE, and FF (various versions of each) in and out of quirks mode. A quick text scan of the "editor's draft" of HTML5 at http://www.w3.org/html/wg/html5/ reveals no mention of either clientWidth or innerWidth, so I'm wondering where this might be handled if not in HTML itself? Apologies if this has been discussed ad nauseum before; I may have been napping. David