You can install the security certificate when using Firefox 3.5 or later, so that the warning dialog box does not appear every time you log on.
From your browser, open ePO - On-prem. The This Connection is Untrusted page appears.
Click I Understand the Risks at the bottom of the page.
Click Add Exception.
Click Get Certificate. The Certification Status information is populated and the Confirm Security Exception button is enabled.
Make sure that Permanently store this exception is selected, then click Confirm Security Exception.
Now when you log on to ePO - On-prem, you are no longer prompted to accept the certificate.