macOS 10.12.1 or newer required to use the Internet problem-free from October 1st

[jagan]

The IdentTrust DST Root CA X3 certificate will expire September 30th.

That means you have to use macOS 10.12.1 or newer to use the Internet problem-free from October 1st.
Many sites will not open with older OS versions.
A possible work-around is to use Firefox (v50+).

More info here:
https://scotthelme.co.uk/lets-encrypt-old-root-expiration/

 

[jagan]

If you still have to use macOS 10.9-11, Firefox 78.xx ESR will still work after October 1st.
(last update planned for October 5th):

Firefox 78.14 ESR

 

[PapaPiccolino]

Hi jagan. Thanks for posting this. I was about to start a thread about my Safari 11.1.2 and Opera 79.xx, which have started having this problem with various sites (I use OS X 10.11 El Capitan). What a pain. My computer is a Mac Pro 3.1, and maxes out with El Capitan. I have a whole bunch of Speed Dials set up in Opera which work great for me. I'm not sure if I can import these Speed Dials into Firefox with the same setup.

Thanks again

 

[iHorseHead]

I am surprised they still support 10.12

 

[Hombre53]

Hi jagan. Thanks for posting this. I was about to start a thread about my Safari 11.1.2 and Opera 79.xx, which have started having this problem with various sites (I use OS X 10.11 El Capitan). What a pain. My computer is a Mac Pro 3.1, and maxes out with El Capitan. I have a whole bunch of Speed Dials set up in Opera which work great for me. I'm not sure if I can import these Speed Dials into Firefox with the same setup.

Thanks again

Try dosdude1's High Sierra or Mojave patchers. Still supports 32 bit software...
Link: http://dosdude1.com/software.html