$.fn.autoCycle = function(classes, seconds) {
	var classes	= classes;
	var seconds	= seconds;
	var l		= classes.length;
	var el		= this;
	randomize();
	return this;

	function randomize() {
		n = el.attr('class');
		while (n == el.attr('class')) {
			n = classes[Math.floor(Math.random()*l)];
		}
		el.attr('class', n);
    		setTimeout(randomize, seconds * 1000);
	}
}

$(document).ready(function() {
  $('#header').autoCycle(['header1','header2','header3','header4'], 15);
});