I updated to 10.9.2 and now SSL is broken. How do I fix this?
Open Keychain Access and delete the DigiCert certificates, but only the ones in the login keychain - not the ones in System or System Roots.

Afterward, you may need to restart your browser and/or network service (switch Airport off and on again, or disable and re-enable Ethernet. If you want to be sure, just restart your computer.

If you're a dummy (like I was) and deleted all the DigiCert entries, you can restore them by manually downloading and installing the 10.9.2 update from Apple.