You may not think about it much as you browse the web every day, but a website's certificate is incredibly important. Your browser handles so much information behind the scenes to make sure you're browsing the web safely.
Sometimes, however, you may see a website certificate error informing you that the Certificate for that website belongs to another.
If you see it all the time, you may have a problem with your system clock or you may have some malware that you need to remove, but if you've only seen it a few times, it's worth looking into the source of the problem.
To view the certificate of any website in any browser (except Edge), click the green lock that appears when you visit a page that uses HTTPS. Select Details –> View Certificate in Chrome, click the arrow and select More Information in Firefox, or select View Certificates in IE. This will allow you to see who owns the Certificate.
However, a Certificate can be valid for more than one URL.
If you view YouTube 's certificate , it appears to be issued to google.com. By going to the Details tab in any browser and finding the Subject Alternative Name , you can see other names for which the certificate is valid.
So, the Google is valid for youtube.com, gmail.com, and android.com, for example.
Using this information to your advantage, you can find out whether an invalid certificate warning comes from a legitimate site name change (perhaps Hewlett-Packard changes its name to Hewlett-Jackson and the site changes from hp.com to hj.com) or whether it's a certificate for some suspicious URL on the other side of the world.
