This error is classified into Critical Safari security errors. Look at our following solution to fix UR97L1DA2TA on Safari completely in Mac OS X.
Mac users face the UR97L1DA2TA error in many different contexts with using Safari. Some encounter this error when they try to log on to a website, and some even fall in trouble when they try to purchase a product online.
How to fix?
I suppose this is an unreliable warning. You should not follow the provided instruction to solve the problem your self. Do the following things instead:
Step 1: Quit the Safari. If you can not, take Force Quit… function in OS X (command + option + esc).
Step 2: Run Safari, then hold the shift key down.
Step 3: Turn the WiFi off and then turn it on again.
Step 4: Delete all Safari Cookies: Safari > Preferences > Privacy > Cookies and other website data > Click “Details” > Remove all cookies.
Get your Safari upgraded to newest version is necessary after all.