There is a bunch of information for webmasters that used to live on Google Plus. Google employees such as John Mueller posted there. We have about 150 posts that link to Google plus:
Google plus is no longer available and those links are broken. They should be removed or the links converted to a cached copy from the internet archive.
I'd appreciate any help with this project. As usual with mass edit projects, please just do a few at a time to prevent flooding the front page.