$(function() {
	$('#main_content').prepend('<div class="ir next">next</div>').prepend('<div class="ir prev">previous</div>');
	$('#slideshow').cycle({
		prev:	'.prev',
		next:	'.next',
		before:	onBefore
	});
});
// callback fired when each slide transition begins
// centres the image within the #main_content div
function onBefore(curr,next,opts) {
    var $slide = $(next);
    var w = $slide.outerWidth();
	var containerWidth = $("#main_content").outerWidth();
    $slide.css({
        marginTop: 0,
		left: '50%',
        marginLeft: -(w / 2)
    });
};