This is going to be a slightly technical post, but helpful for you if you’re experiencing any “certificate error” issues.
Have you visited Facebook lately and gotten an error like “This is probably not the site you are looking for!”, or something about the certificate being invalid, etc? Â Or Gmail? Â Or any other site that you’ve used the https:// protocol? Â There are a few possibilities for what is going on; I’ll explain three, and how to fix one.
The first, one from which your browser is trying to protect you, is the possibility that someone has hijacked a DNS server or is placing themselves between you and the web site you are trying to reach, pretending to be that web site to eavesdrop on your information. Â (The job of a certificate is to prevent that). Â This is bad. Â You want to heed this warning and stay away from the site, as someone could steal your username, password, or any other information you’re sending to the site.
The second, another from which your browser is trying to protect you, is a virus/spyware program has attempted to hijack the internet traffic from within your own computer. Â Install anti-virus/anti-spyware to fix it.
The third (and the one which white I’m going to try to help you) is that your computer’s DNS cache is someone out of date, and that it is trying to access the wrong server (innocently).  I should probably tell you what a DNS server is.  A “Domain Name Server” is a computer that converts domain names (like google.com) into IP addresses (like 66.102.7.99).  Sometimes, your computer or browser will cache this information so that your browsing experience goes faster.  If these numbers are out-of-date, however, you’ll get that certificate error.  Here’s how I fix it.
- First and foremost, try quitting and reopening your browser. Â If going to the website still results in an error, continue to step 2.
- Mac: Quit your browser. Â Open the Terminal App, and type the following command (without the quotes, of course): “dscacheutil -flushcache”. Reopen the browser.
PC: Quit your browser. Â Open the Command Prompt, and type the following command (again, without the quotes): “ipconfig /flushdns”. Â Reopen the browser.
Now, if that doesn’t work, there’s a chance there’s something wrong with your DNS server settings, and you might want to contact your DSL or cable company to get a fix. Â Good luck!