function popup(url, name, width, height, params)
{
	if (width == 0) width = 600;
	if (height == 0) height = 450;
	posX = (screen.width / 2) - (width / 2);
	posY = (screen.height / 2) - (height / 2);
	options = "screenX="+posX+",screenY="+posY // Netscape
			+",left="+posX+",top="+posY // IE
			+",width="+width+",height="+height;
	if (params != "") {
		options += "," + params;
	}
    newWin = window.open(url, name, options);
	newWin.focus();
}