function popup(name,width,height)
{
var topPos = (screen.height-height)/2
var leftPos = (screen.width-width)/2
var popup = window.open("","Images","width=" + width + ",height=" + height + ",top=" + topPos + ",left=" + leftPos + ",toolbar=0, status=0, menubar=0, resizable=0, scrollbars=no, directories=0, dependent=yes");
popup.document.open();
popup.document.write("image popup");
popup.document.close();
popup.focus();
}
function switchImg()
{
document.images[1].src = document.images[0].src
}