function changeClass(obj, new_class)
{
    obj.className = new_class;
}

function changeBgColor(obj, new_color)
{
	obj.style.backgroundColor=new_color;
}

function changePic(name, pic)
{
	name.src = pic;
}

function popup(url, name, width, height)
{
	left_pos = (screen.width / 2) - (width / 2);
	top_pos = (screen.height / 2) - (height / 2);
	options = '';
	if (height > screen.height) {
		height = screen.height - 20;
		top_post = 10;
		options = 'scrollbars=yes,';
	}
	
	window.open(url, name, options  + 'width=' + width + ',height=' + height + ',left=' + left_pos + ',top=' + top_pos);	
}