hi ralphie0683, first please make sure that the date, time & timezone are set correctly on your system. if this doesn't solve the issue (or it is already set properly), a solution depends on the individual circumstances:

• what is the error code shown when you click on advanced on that error page?
• please also give us more information about the error by clicking on the error code, copying the text to the clipboard and then pasting it here into a reply in the forum.

thank you!

Your connection is not secure

The owner of search.yahoo.com has configured their website improperly. To protect your information from being stolen, Firefox has not connected to this website.

This site uses HTTP Strict Transport Security (HSTS) to specify that Firefox may only connect to it securely. As a result, it is not possible to add an exception for this certificate.

Learn more…

Report errors like this to help Mozilla identify and block malicious sites

hi, that's the same information like in your original post. without knowing more about the error code that is displayed, i'm going to guess that you are most likely seeing this: How to troubleshoot security error codes on secure websites