I've added 'window.onbeforeunload' to test a weird behavior of IE<=8 (actually I could tweak the JS on the page to add the listener only for old IE). When you have a link like '<a href="javascript:void(0);">' + onbeforeunload + click event listener bound to <a> doesn't return false, then clicking (from mouse/kbd) such a link triggers onbeforeunload().

It's documented under http://jakub-g.github.io/accessibility/onclick/#note6