Allow Internet Explorer 8 shutdown behavior

This policy setting allows you to revert to the Internet Explorer 8 behavior of allowing OnUnLoad script handlers to display UI during shutdown. This policy setting may be needed to fix compatibility problems with particular web applications. If you enable this policy setting OnUnLoad script handlers display UI during shutdown. If you disable or do not configure this policy setting OnUnLoad script handlers do not display UI during shutdown (default behavior in Internet Explorer 9).