Please clear your browser cache, which stores files that can cause errors like this one. There are links below to instructions for cache clearing on the most popular browsers.
Google Chrome Steps (You DO NOT need to check the "Cookies and other site data" box. This will sign you out of all websites.)
Mozilla Firefox Steps
Important: Once done, please close all browser windows, then reopen and see if the problem persists.
Please reach out to support@secondstep.org if you continue to receive an error.