// SwitchNav
//	sButton:    ID of navigation image (icon), that was clicked
//	sElement:	ID of element (<DIV>,<TABLE> etc.), which is to show or hide
//	sPlus:      URL of image file for collapsed-icon
//	sMinus:     URL of image file for expanded-icon
function SwitchNav(sButton,sElement,sPlus,sMinus) {
	if (document.getElementById(sElement).style.display=="none") {
		document.getElementById(sElement).style.display="block";
        document.getElementById(sButton).src=sMinus;
    }
    else {
		document.getElementById(sElement).style.display="none";
        document.getElementById(sButton).src=sPlus;
    }
}