HTTPS and OCSP Stapling for Apache

"OCSP Stapling" is a way of caching part of the SSL verification process on a websever in an HTTPS connection.

Its caches a certificate check with the certificate authority, instead of doing it for each request.

Here's how to enable it

# server config or virtual host
SSLStaplingCache shmcb:/tmp/stapling_cache(128000)
SSLUseStapling on

And this amazingly thorough test enables you to check you've set this, and pretty much everything else,  correctly