var ids=new Array('a1','a2','a3','a4', 'a5', 'a6', 'a7', 'a8', 'a9', 'a10', 'a11' );

function switchid(id){	
	hideallids();
	showdiv(id);
}

function hideallids(){
	//loop through the array and hide each element by id
	for (var i=0;i<ids.length;i++){
		hidediv(ids[i]);
	}		  
}

function hidediv(id) {
	//safe function to hide an element with a specified id
		document.getElementById(id).style.display = 'none';
	}


function showdiv(id) {
	//safe function to show an element with a specified id
		document.getElementById(id).style.display = 'block';
}