var previover = 0;

function imageover(iover) {
if (iover != previover) {
document.getElementById('image'+iover).style.display="block";
document.getElementById('arrow'+iover).style.display="inline";

	if(previover!=0) {
	document.getElementById('image'+previover).style.display="none";
	document.getElementById('arrow'+previover).style.display="none";

}
previover = iover; 
}
}