Warning! You're being spied on!
Your Internet Service Provider (ISP) seems to be running a Deep Packet Inspection advertising system. What this means is that all of your internet browsing is being intercepted and spied upon, and information about your interests is being sold so that adverts can be sent to you.
You probably weren't aware that this was going on - the change to your terms and conditions that you may have agreed to will have claimed that you were going to get added protection from internet security threats, and won't have mentioned much about the privacy abuse that was involved.
Alternatively, someone else in your household may have signed you up for this 'service' without you realizing.
On the other hand, maybe you like having a dubious corporation looking through everything that you do online. Even so, the website you were trying to visit has decided that it does not consent to having its content used for commercial profit by spyware companies, which is why you are seeing this page. Sorry.