I am working on an old site of mine, and it has an old "Google Fusion" button. I don't remember what it did, but I think it allowed people to bookmark the RSS feed in their account? The button no longer works (just goes to the Google homepage). I have been trying to find some information about the new protocol for allowing people to bookmark a page in their Google account by clicking a button on your site (or is this completely obsolete now?).
I know this seems very elementary, but it's not something I've kept up with.