How can you figure out the highest z-index in your document?

Question

In order to set a div containing a transparent text image as the highest z-index in my document, I picked the number 10,000 and it solved my problem.

Previously I had guessed with the number 3 but it had no effect.

So, is there a more scientific way of figuring out what z-index is higher than that of all of your other elements?

I tried looking for this metric in Firebug but couldn't find it.

Answer 1

Stealing some code from abcoder site for the sake of clarity:

  var maxZ = Math.max.apply(null, 
    $.map($('body *'), function(e,n) {
      if ($(e).css('position') != 'static')
        return parseInt($(e).css('z-index')) || 1;
  }));