Sarah noticed an issue with all the site pages on IE7: the page style was sometimes overridden by a very plain style suitable for printing. Investigation revealed that IE was actually trying to do the right thing; our list of stylesheets, most of which were supposed to be alternate stylesheets, were listed as regular stylesheets. This was related to the JavaScript code which enables the user to choose specific stylesheets. Setting the alternate stylesheets to rel="alternate stylesheet" fixes the IE problem, and also, surprisingly, doesn't seem to break the enabling/disabling functionality. I added in an eighth stylesheet link with media="print" so that the print stylesheet is always used for printing, as well as being selectable for display.

All this stuff might need some more thought down the line, but it all seems to be working correctly at the moment.