// getPageScroll() by quirksmode.com
function getPageScroll() {
   var xScroll, yScroll;
   if (self.pageYOffset) {
      yScroll = self.pageYOffset;
      xScroll = self.pageXOffset;
   } else if (document.documentElement && document.documentElement.scrollTop) {	 // Explorer 6 Strict
      yScroll = document.documentElement.scrollTop;
      xScroll = document.documentElement.scrollLeft;
   } else if (document.body) {// all other Explorers
      yScroll = document.body.scrollTop;
      xScroll = document.body.scrollLeft;
   }
   return new Array(xScroll,yScroll)
}

// Adapted from getPageSize() by quirksmode.com
function getPageHeight() {
   var windowHeight
   if (self.innerHeight) {	// all except Explorer
      windowHeight = self.innerHeight;
   } else if (document.documentElement && document.documentElement.clientHeight) { // Explorer 6 Strict Mode
      windowHeight = document.documentElement.clientHeight;
   } else if (document.body) { // other Explorers
      windowHeight = document.body.clientHeight;
   }
   return windowHeight
}

function popup()
{
   $('#overlay').css({
      height: $(document).height(),
      // opacity: 0.7
   }).show();

   $('.popup').css({
      top: getPageScroll()[1] + (getPageHeight() / 3.2),
      left: $(window).width() / 2 - 225,
      // opacity: 1.0
   }).show();
}