So glad to see Flag-fox available for versions 57+. (I am using Nightly versions 59+). This add-on was the one I missed the most. Thank you Dave G. for your effort and time to convert the add-on from older version. This add-on is a must. It is very convenient to know were the servers of a site are located before you do business with them. Also, the "Is it up?" option lets you know if the a site you are trying to access is down on their end or if you have a problem on your end. I recommend this add-on to all Firefox users.