function img_show(id) {
    var e = document.getElementById(id);
    if (!e)
	return;
    e.style.display = "block";
}

function img_hide(id) {
    var e = document.getElementById(id);
    if (!e)
	return;
    e.style.display = "none";
}

function img_toggle(id) {
    var e = document.getElementById(id);
    if (!e || !e.style)
	return;
    if (e.style.display == 'none' || e.style.display == '')
	return img_show(id);
    else
	return img_hide(id);
}