function Get_Obj(id){
 var o=new Object();
 o.o=(document.getElementById) ? document.getElementById(id) :
 document.layers ? document.layers[id] :
 document.all ? document.all[id] : null;
 o.s=document.layers ? o.o : o.o.style;
 return o;
}

function toonLaag(id){Get_Obj(id).s.visibility = 'visible';}

function wegLaag(id) {Get_Obj(id).s.visibility = 'hidden';}

function wegLagen() {for (var i=0; i<arguments.length; i++) wegLaag(arguments[i]);}

function allesweg(){wegLagen('l1','l2');}