function switch_product_img(divName, totalImgs) {
for (var i=1; i<=totalImgs; i++) {
var showDivName = 'photo_' + i;
var showObj = document.getElementById(showDivName);
if (showDivName == divName)
showObj.style.display = 'block';
else
showObj.style.display = 'none';
}
}