Security alert issue?

I am definitely not the most techno savy person, and this just confuses me. Whenever i log into league, i get a security alert message. It says " a secure connection with this site cannot be verified. Would you still like to proceed? The certificate you are veiwing does not match the name of the site you are trying to veiw." When i log out of league, the same message pops up but then it does not respond, and crashes league. I have looked at many other posts from a few years ago about turning off certificates in IE, and i did that, and it worked for a few minutes, then it started up again. As i said before, im not techno savy, and i have no clue what to do.. Can someone please help?