CSS1 worked:
.parentDisable { z-index:2000; width:100%; height:100%; display:none; position:absolute; left:
Instead of position: absolute use position: fixed.
position: absolute
position: fixed
To prevent the page from jumping to top you need to include a return false within your javascript-function hidePopup_.
return false
hidePopup_
The link trys to jump to the anchor # and since there isn't one, it jumps to the top.
#