The page you are trying to view cannot be shown because the authenticity of the received data could not be verified."

Within the past 24 hours there's been a Firefox update installed which, as usual, has happened quietly and without issue, so I know that my browser is safe and up-to-date. However, today I headed to one of my favourite sites - Imgur - only to find a blank page. Well, not entirely blank - all the words and frames and bits are there but no photos or videos - nothing visual. I had to ignore it during the day and then this evening I asked Imgur if they knew what the problem was. They replied: "It looks like your ISP may be blocking access. I was able to confirm your ISP as TalkTalk which has had this issue occur in the past. I'd recommend reaching out to them directly or using an alternative connection to the site, if possible." Fair enough - it's TalkTalk's problem - or is it? Soon afterwards I looked at a comment in Reddit and they gaive a link to Imgur - so, not really expecting much, I clicked on the link. ''Secure Connection Failed An error occurred during a connection to i.imgur.com. PR_CONNECT_RESET_ERROR The page you are trying to view cannot be shown because the authenticity of the received data could not be verified." Please could you add your comments so that I can be assured that it is indeed my server's fault and not a browser problem - so that I can get to the bottom of this unwanted security query.