function toggleLayer(whichLayer)
{
if (document.getElementById)
{
// this is the way the standards work
var style2 = document.getElementById(whichLayer).style;
style2.display = style2.display? "":"block";
}
else if (document.all)
{
// this is the way old msie versions work
var style2 = document.all[whichLayer].style;
style2.display = style2.display? "":"block";
}
else if (document.layers)
{
// this is the way nn4 works
var style2 = document.layers[whichLayer].style;
style2.display = style2.display? "":"block";
}
}

function toggleLayer_image(whichLayer)
{
if (document.getElementById)
{
// this is the way the standards work
var style2 = document.getElementById(whichLayer).style;
style2.display = style2.display? "":"block";
if (style2.display=="block"){
      document.getElementById(whichLayer + '_image').src="images/minus.gif";
    }else {
      document.getElementById(whichLayer + '_image').src="images/plus.gif";
    }

}
else if (document.all)
{
// this is the way old msie versions work
var style2 = document.all[whichLayer].style;
style2.display = style2.display? "":"block";
}
else if (document.layers)
{
// this is the way nn4 works
var style2 = document.layers[whichLayer].style;
style2.display = style2.display? "":"block";
}
}