YouTube is getting ready to make an important change, by letting people watch the site’s videos even when they’re not connected to the Internet. Google announced the move in a vague blog post late Tuesday night, and I gave you a little more detail about how it will work this yesterday: You’ll need to use a YouTube mobile app to watch the videos, which will contain ads. You’ll have up to 48 hours to watch the stuff you take offline. Now here’s a bit more detail about Google’s plans, via a e-mail YouTube sent out to “partners” — YouTube uploaders it has a commercial relationship with. Most of the new stuff here deals with the logistics of the online/offline transfer. It’s also worth noting that YouTube says this does not apply to the movies and TV shows it offers for rent and purchase.