Notes from the Google Webmaster Hangout on the 3rd of November, 2017.
Expired Content Can be Redirected, 404'd or Noindexed
There is no one correct way to deal with expired content on a site. If there is a relevant page that replaces the expired one then you can implement a 301 redirect. If there is no replacement page, then you can leave the page as 200 saying that it is no longer valid and use either a 404 or noindex after a period of time.
Microsites Can Be Seen as Doorway Pages
Microsites often look like a collection of doorway pages. If you are looking to build these microsites up in the long run then this might be an option, but if they don’t have value beyond driving traffic to another site, then microsites aren’t recommended for search and should be noindexed.
Mixed Migrations May Cause Google to Index HTTP or HTTPS URLs
Forgetting to update your sitemap files following a HTTPS migration could cause some pages to be indexed with the HTTP URL and some HTTPS.
Google Given Conflicting Signals if HTTP & HTTPS Pages Are Present Google Uses Multiple Signals to Choose HTTP or HTTPS URLs
Redirects, internal links, sitemaps, rel canonicals are taken into consideration when Google chooses to index a page on HTTP or HTTPS. Internal links to HTTP URLs after a migration to HTTPS will give Google conflicting signals, but usually there will be enough signals to indicate that the HTTPS version should be indexed.
Rel Canonical Isn't Required For Paginated Pages
If pagination is added to a page with rel next and rel previous it isn’t necessary to add a rel canonical to the page itself but it’s good practice.
Google Isn't Always Able to Show Cached Version of a Page
Tag Pages Are Usually Seen as Low Quality
Tag pages are usually low quality and look like search results pages, so it doesn’t make sense for Google to show them in search results and the prefer to show pages with content.