Security Warning Inconsistencies

[Anak]

I bought my DW a Nook Color (NC) two years ago:
Model - BNRV200
Software version - 1.4.3

Just last month she started receiving a security warning when she would try to visit a web site from an email:

   Warning

Security Warning
There are problems with the security certificate for this site.
This certificate is not from a trusted authority.

​

She can then either Cancel, View Certificate or Continue.

Cancel takes her back to the emails.
It will not let her view the certificate.
If she knows it is safe it will let her continue on to the web site.

Image is from the Nook device:


I did ask about this on a Nook forum and this is the reply I received:

Message:
-----
basically the web site has an invalid certificate for secure (https) transfer. Could be their certificate expired or something else. If continue works then just do it and/or contact the website. If this is your bank or something like that I'd be careful. Only the web site with the bad certificate can fix it; not a nook thing.
-----

But, Here is the inconsistent part:
These warnings do not appear when accessing these same sites from our desktop.

Can anyone explain what is going on here. Is it or is it not a "Nook thing", and how to correct it?
One thing I will try is, ask the DW to clear the cache, form data, and cookies on the NC and see if that helps.

I will also be contacting Barns&Noble personally to see what they have to say.

 

[UsernameIssues]

....But, Here is the inconsistent part:
These warnings do not appear when accessing these same sites from our desktop............

You could be redirected to a different web server based on the user agent.

In other words,
the desktop tells the server that it is a desktop (via the user agent)
...it gets its webpages served up from the main web server
the nook tells the server that is is a mobile device
...it might get redirected to a different web server (with different certificates)

That said, I see this same warning sometimes when browsing from my cell phone and yet the warning comes and goes in from day to day. I've wondered if that is due to hitting different servers as part of a load balancing scheme.

The caveat to all of the info above is: I could have it all wrong