Might be useful for debugging ("where is this f*ing margin coming from?!?").

document.getElementsByStyle()

/*! document.getElementsByStyle()
 * 
 * Returns an array (not a NodeList!!) containing all elements matching certain 
 * computed style rules.
 *
 * Usage:
 * var blockElements = document.getElementsByStyle('display: block');
 * 
 * PS: I know it might not be the best idea to extend HTMLElement/HTMLDocument since it
 * returns an array not a NodeList (like getElementsByTagName). But I recommend to use
 * it for debugging purposes only, it's slow!
 *
 * @author Manuel Bieh
 * @url http://www.manuelbieh.com/
 * @version 1.0.0
 * @license MIT
 *
 */

;(function(window) {

	var getElementsByStyle = function(style) {

		var elements = this.querySelectorAll('*');
		var matched = [];
	
		style = style.split(':');
		var prop = style.splice(0,1)[0];
		var value = style.join(':').replace(/^\s*/g,'').replace(/(\s|;)*$/g, '');
	
		for(var i = 0; i < elements.length; i++) {
	
			var el = elements[i];
			var propVal = window.getComputedStyle(el).getPropertyValue(prop);
	
			if(propVal === value) {
				matched.push(el);
			}
	
		}
	
		return matched;
	
	}

	var extend = [HTMLDocument, HTMLElement];
	extend.forEach(function(obj) {
		obj.prototype.getElementsByStyle = getElementsByStyle;
	});

}(this));