Created attachment 72380 [details] a simple test page that demonstrates and describes the problem In some cases it's possible to click on things behind the onbeforeunload navigation confirmation dialog. This only appears to happen if you click on a link or something on the page that triggers the onbeforeunload dialog (not when refreshing the page, even by clicking the refresh button, or using the keyboard to activate a link on the page). Then you can only click one thing on the page, and after that the dialog take focus and acts like a normal modal dialog. One exception is that if you click a link again, another navigation confirmation dialog appears and you can click on one more thing in the background. So by repeatedly clicking a link you could bring up as many of these dialogs as you want. I've only tried this on windows (7 and XP), so I'm not sure if it is an OS specific problem. I was able to simulate the problem in Safari 5.0.2 (7533.18.5) and the WebKit-r70599 nightly build. I could not simulate this problem in Chrome 7.0.517.41 (and not in Firefox or IE8 either). See the attached test page for some example steps to simulate the problem.