After five years of warnings, Google is finally ending support for the old version of Google Sites on December 1st. If you’ve been clinging to the hope that Google wouldn’t force you to transition to the current version of Google Sites, it’s time to give up that hope and convert your old site to the current version of Google Sites. Otherwise, on December 1st you’ll no longer be able to edit your site or do anything else with it.
On a related note, I have a complete playlist of Google Sites tutorials right here. The best video to get started is this one that walks you through everything you need to know to create your first website with Google Sites.