I made an absolute tinny code to find the highest z-index of absolute DIV
to show my shouting box and to make it appear absolutely at the top of all html elements.

I used selector of ”body > *‘ instead of ‘body *‘.

”body > *‘ means all tags/elements which are found at first depth of
whether ”body *‘ selects all tags/elements at any depth.
It doesn’t matter what’s is the maximum/highest z-index of an absolute element
rather it matters what’s the maximum/highest z-index of the absolute elements
which are next to in first depth only to show the shouting box on top most strata.

N.B. Shouting box is appended to document.body in this case.

//include jQuery.js --  visit: http://jquery.com/
$(function(){
    var maxZ = Math.max.apply(null,$.map($('body > *'), function(e,n){
           if($(e).css('position')=='absolute')
                return parseInt($(e).css('z-index'))||1 ;
           })
    );
    alert(maxZ);
});