In April of 2009, Apple announced the pending discontinuation of its .Mac Homepage service. A formal date was set in October, and that date is today.
Your sites won't be gone for good, however. To find them, open your iDisk and navigate to the Sites folder. There you'll find all of the HTML pages that made up your Homesite. Likewise, pictures and movies will be found in the Pictures and Movies folder.
Note that publishing with iWeb will not be affected by this change. So long, Homepages! Thanks for all the fish.