Given a template where the HTML cannot be modified because of other requirements, how is it possible to display (rearrange) a div
above another div
As others have said, this isn't something you'd want to be doing in CSS. You can fudge it with absolute positioning and strange margins, but it's just not a robust solution. The best option in your case would be to turn to javascript. In jQuery, this is a very simple task:
$('#secondDiv').insertBefore('#firstDiv');
or more generically:
$('.swapMe').each(function(i, el) {
$(el).insertBefore($(el).prev());
});