var OP = (window.opera) ? 1:0; 
var IE4 = (document.all && !OP) ? 1:0; 
var IE5 = (IE4 && document.getElementById) ? 1:0; 
var NN4 = (document.layers) ? 1:0; 
var NN6 = (!IE4 && !NN4 && document.getElementById) ? 1:0; 
var NOT = (!OP && !IE4 && !IE5 && !NN4 && !NN6) ? 1:0; 

function setLayerStatus(doc, layerName, visible){
	if (NN4==1){ 
		//Netscape 4
		doc.layers[layerName].display 				= ( ( visible ) ? "block" : "none" )
	}else if(NN6==1){ 
		//Netscape 6.x, Firefox
		doc.getElementById(layerName).style.display 	= ( ( visible ) ? "block" : "none" )
	}else if ((IE5==1)||(IE4==1)){ 
		//Explorer
		doc.all[layerName].style.display			= ( ( visible ) ? "block" : "none" );
	}
}