It's giving you an error because it's not a trusted certificate.
You have 2 options (well 3).
Ignore it, continue to bypass the warning.
Import it in to each browser you want to trust it on
Replace the certificate with a valid one - depending on the way the system works with certificates, this could be 2 minutes of your time or a nightmare.
Also, if you want to, in Chrome when you get the error - whilst on the same screen, simply type 'thissisunsafe' anywhere on the page and the warning will go away, though this should be a last resort.
