Hi Amish
I really would be interested what causes this problem. My browser is based on the up to date Firefox 52.9 ESR, i.e. extended support release. Everything newer is always kind of beta. The error message above states your Firefox wasn't able to connect "securely". That means it tried the connection via https if I understand it right, and that is not yet possible here. If you're using a newer Firefox version and the message is caused by this, you should see it at other pages, too. Have you tried i.e. Englishbob's page
http://www.morphography.uk.vu/ ? It is http only still as well. If this is the problem you should see the message there, too. Or it may be caused by some installed extension. I have ABP, NoScript and HTTPs Everywhere running.