This works perfectly for me in both Chrome and Safari:
<html><body><p>Test</p>
<script>window.onbeforeunload = function() { return "Sure?"; }</script>
</body></html>
When I try to close the window, I get the prompt.
This works perfectly for me in both Chrome and Safari:
<html><body><p>Test</p>
<script>window.onbeforeunload = function() { return "Sure?"; }</script>
</body></html>
When I try to close the window, I get the prompt.