function toggle_showgrid() {
	var d = document.getElementsByClassName('container');
	for (var i = 0; i < d.length; i++){
		if (d[i].className.indexOf('showgrid') == -1) {
			d[i].className = d[i].className + ' showgrid';
		} else {
			d[i].className = d[i].className.replace(/showgrid/,'');
		}
	}
	void(0);
}