Adds transparent background to every node in the DOM. Allows for easy collision and overlap inspection. Ctrl-i toggles functionality.

DOMHighlight.js

// DOM Highlight (Ctrl-i)
$(function() {
	$("<style type='text/css'> .DOMHighlight {background: rgba(0,0,0,0.1);} </style>").appendTo("head");
	$('body').keypress(function(e) {	
		if (e.which === 9)
			$('*').toggleClass('DOMHighlight');
	});
})();