[BUG #8229] Removed the special implementation for IE browsers to use an additional iframe element to block the element. This is not necessary anymore.
[BUG #8229] Changed implementation how to block the whole document. Now the DIV element is added as first child of the body with 'position:fixed' and '100%' for 'width' and 'height'.
This ensures that the whole document is blocked no matter how big the possible scrollable document is and it adapts on resize without any additonal JS code.