To install the Certificate Authority certificate in firefox 3 on windows:
Download cacert.pem from the parent page.
From the Tools > Options dialog - choose the Advanced Tab, then the Encryption sub-tab:

On this tab choose the "View Certificates" button, then on the dialog that pops up, choose the Authorities tab:

Choose the import button and select the downloaded cacert.pem. Check all checkboxes and confirm:
Download the .p12 format certificate. Make sure that it is called cacert.p12 - not cacert.htm or cacert.p12.htm. If you have file endings hidden this may happen. If the icon looks like an Internet Explorer one then the file has the wrong name.
Choose Tools > Options then the content tab:

Choose the certificates button, then the Trusted Root Certification Authorities tab:

Safari and Apple Mail use the system keychain.
Open the Keychain Access application (Applications > Utilities) and simply import the cacert.pem file. On Leopard it should be installed to the system keychain, on tiger to the x509anchors keychain.
I believe that for https in Safari it will work in the Login keychain - but I don't think it will work for Apple Mail there.
To install the Certificate Authority certificate in firefox 3 on the mac:
Download cacert.pem from the parent page.
From the Preferences dialog - choose the Advanced Tab, then the Encryption sub-tab:

On this tab choose the "View Certificates" button, then on the dialog that pops up, choose the Authorities tab:

Choose the import button and select the downloaded cacert.pem. Check all checkboxes and confirm:
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