Hello jerusha992 and welcome to Apple Support Communities.
It appears you are having some difficulty with a security certificate coming up as "not trusted" on your iPhone and it appears that the site in question is one associated with Wi-Fi service provided by British Telecom.
How to forget a Wi-Fi network on your iPhone, iPad, iPod touch, or Mac
There is nothing a user can do to take care of the certificate as it has to be renewed by the domain owner. The most likely cause of the warning coming forward is that, at some point, you connected to a BT public Wi-Fi network. Once that has happened, if you get in range of the network again, the iPhone will try to connect to it as a known network.
The webpage listed in the security warning appears to be the one you would use to accept terms and log-in to a BT Wi-Fi network. If you forget that network, the system won't try to load that link as a part of the network sign-on and you should stop seeing the warnings.
Cheers.