If you have your own server in your office, you are likely to come across Certificate Errors from time to time. This is caused because although communications with your server is secured (with SSL), no certificate from an authority has been purchased. Commercial sites tend to pay for certificates, but because your site is only used internally, it was deemed unnecessary to purchase one.
Therefore you may get one of two messages:
If you get the above message (or similar), just click on Don't ask me again and click Connect. This message may repeat more than once
You may also get a message from Avast antivirus like this:
If so, just click Confirm Security Exclusion
Once, you've done this, you should not have to do it for a while, but every few months you may be asked to re-do either or both of the above.