var currlayerId = "leftContent"; 

function toglayer(id) 
{ 
if(currlayerId) setDisplay(currlayerId, "none"); 
if(id)setDisplay(id, "block"); 
currlayerId = id; 
} 

function setDisplay(id,value) 
{ 
var elm = document.getElementById(id); 
elm.style.display = value; 
}