var prefix = 'img/navigation/';
function _nni(element,new_image) {
	if(element) {
		element.src = prefix+new_image+'.gif';
	}
}


function layer_open(elename) {
	var ele = document.getElementById(elename);
	ele.style.display = 'block';
}

function layer_close(elename) {
	var ele = document.getElementById(elename);
	ele.style.display = 'none';
}