jQuery mouseleave not firing when mousing into another overlapping browser window
<p><strong>How do I detect whether a page is visible to the user, even if it doesn't have the focus?</strong>  </p>

<p>Using timeout events to check whether or not there has been mouse activity in the window is not a viable solution.</p>

<p>I'm attempting to detect when a page is visible using JavaScript/jQuery.  The environment is such that the user will have multiple pages open in multiple windows (side-by-side).  Using the $(window).focus()/blur() approach doesn't work well - as soon as I change the focus to another window, it blurs the other page.  I need it to still recognize that it's open and visible to the user.</p>

<p>I've also tried to use the jQuery $(window).hover(), .mouseleave(), and .mouseenter() events.  I've noticed an interesting behavior where these events don't fire when you mouseout of the window into another browser instance!  <em>Bonus points available for anyone who can explain that behavior.</em></p>
