function toggleFrame (layer_name,img_name)
{
var layer = document.getElementById(layer_name);
var current_state = layer.style.display;
var img = document.getElementById("img_" + layer_name);

if (current_state == "none")
{
	layer.style.display = "block";
	img.src = "images/nav/minus.gif";
}
else
{
	layer.style.display = "none";
	img.src = "images/nav/plus.gif";
}
}