Cross-browser event bubbling.

gistfile1.js

var body = document.getElementsByTagName('body')[0];
var captureEvent = function(e) {
	var target = e.target || e.srcElement;

	if (target.nodeName === 'A') {
		alert(target.getAttribute('data-track'));
	}

	return false;
};

if (!body.addEventListener) {
	body.attachEvent('onclick', captureEvent);
} else {
	body.addEventListener('click', captureEvent, false);
}