I get the same problem. This could be a website issue.

There is security software like Avast, Kaspersky, BitDefender and ESET that intercept secure connection certificates and send their own.

https://support.mozilla.org/en-US/kb/firefox-cant-load-websites-other-browsers-can

https://support.mozilla.org/en-US/kb/firefox-and-other-browsers-cant-load-websites

https://support.mozilla.org/en-US/kb/secure-connection-failed-error-message

https://support.mozilla.org/en-US/kb/connection-untrusted-error-message

Websites don't load - troubleshoot and fix error messages

http://kb.mozillazine.org/Error_loading_websites

What do the security warning codes mean

I've tried with another browser and there's any issues with it

I tried Windows Internet Explorer and Microfoft Edge:

Hmmm… can't reach this page It looks like the webpage at https://danielesirangelo.altervista.org/ might be having issues, or it may have moved permanently to a new web address.

ERR_SSL_UNRECOGNIZED_NAME_ALERT

You need to use the HTTP protocol to access this website.

• http://danielesirangelo.altervista.org

If you use an extension that forces a secure HTTPS connection then make an exception.

• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems