function layerVis(id,dir) {
    if (document.layers) {
        v = (dir == "on") ? "show" : "hide";
        //document.layers[id].visibility = v;
    }
    else if (document.all) {
        v = (dir == "on") ? 'visible'	: 'hidden';
        document.all[id].style.visibility = v;
    }
    else if (document.getElementById) {
        v = (dir == "on") ? 'visible' : 'hidden';
        document.getElementById(id).style.visibility = v;
    }
}
var lastClicked=null;

function clickOnOrOff(id,url){
	if(document.layers){
		if (lastClicked==null){
			layerVis(id,"on");
			lastClicked=id;
		}
		else if(id==lastClicked){
			layerVis(id,"off");
			lastClicked=null;
		}
		else{
			layerVis(lastClicked,"off");
			layerVis(id,"on");
			lastClicked=id;
		}
	}
	else{
		document.location=url;
	}

}