Just to show we're not biased and all's fair in directory land. Here is an excellent post from Yells head of Web Engineering, Steve Workman.
HTTPS is the secure version of your normal www web pages, and can be seen in your browser as a padlock. eg:
Yell spent 7 months transitioning to HTTPS, which coincidently turns out to be around the same as we did.
This would have proved to be a good guide, so if anyone is considering the ins and outs of migrating their web site, big or small, then this article is a good place to start.