BPL's SSL certificate has expired, and your browser might be warning you about this problem.
Short version: Tell your browser to trust BPL's expired SSL certificate, but don't do that routinely, especially for more important web sites, like your bank.
What does this mean? What should you do about this? What should BPL do about this?
SSL encrypts information between your browser and a web site to prevent snooping by most Bad Guys. SSL typically protects your username and password as you login, and other critical information like credit card purchases, bank account information, and email. This is A Good Thing.
For SSL to work properly, the web site (BPL) needs to buy an SSL certificate from a widely recognized authority. SSL certificates have an expiration date. BPL's has expired. Likely, someone forgot to renew.
An expired SSL certificate still encrypts your username and password, it's just less "trustworthy" in some theoretical sense. I've used expired SSL certificates on many internal systems for many years.
You can tell your web browser to trust the expired BPL SSL certificate, and move on to worry about more important things, like how many cups of water you can boil on one Esbit tablet under perfect lab conditions :-)
HOWEVER - you should NOT routinely ignore SSL warnings from your web browser, and blindly trust whatever comes along. Bad Guys might be impersonating something important, like your bank or email provider.
BPL should renew their SSL certificate, so we, the paying customers, don't have to deal with this nonsense. SSL certs are as cheap as $10 per year.
For the uber-security geeks out there: Yes, I dramatically simplified a complex situation, and you might disagree with my recommendations. Consider using this as a teaching moment for non-security geeks, rather than flaming me with trivia.