Although they all supposedly conform to one or more of the dialects of the same ECMA standard each different browser has its own unique implementation of the Javascript interpreter and there are differences and even a few outright incompatibilities among them. While the Mozilla Javascript interpreter that undergirds Firefox was the original and the base standard there can be incompatibilities, especially if the original target browser was Internet Explorer which has its own dialect called JScript. Try a different browser, I would suggest
Google Chrome, and see if you have the same issue.
