"Your connection is not secure" notice in Firefox

[bullwinkle]

I recently was hit with a virus.  My computer repairman kept whatever information he could, but had to reformat the HD.  I reloaded the latest version of Firefox and it has been fine for four days, but today I get this message for every bookmark - even Amazon.  It allows me to make certain certificate exceptions, but not for everything.  If I type in a website, I get the same thing.

I have Avast as my antivirus software.

My system: 
Windows 7 Ultimate
memory 4GB
297GB HD
64 bit system
This is a SONY laptop VGN-CS110E
Intel Centrino CPU

Thanks

[bullwinkle]

Don't ask me why, but today everything works...every site is now available.

!?!?!??!?!?!?!!???!?

I've always believed that this stuff is magic, having worked in the field for 17 years.

[patio]

      

[Geek-9pm]

Fr what it is worth...
Recently some web sites have been slow to update  the SSL.
The SSL is a method to ensure that the web site is legal and secure.

It is not because of  anything you did. The Webmaster has been lazy.
See here:
https://www.youtube.com/watch?v=ntVeD1sQDsg
Not just Chrome, bet Firefox and other browsers now alter users.
When the Webmaster gets back to work, the problem goes away.    

[VintronNZ]

Hi
One cause of this is that the date/ time are wrong say the year is 2017 instead of 2018 there fore the certificates for web sites don't match your laptops time. Windows at some stage could have validated your clock with an internet time standard and sorted it for you. 

[BC_Programmer]

The SSL is a method to ensure that the web site is legal and secure.

SSL does neither of these things.