Notes from the Google Webmaster Hangouts on the 9th of September, 2016.
Hidden Links are Counted
Links which aren’t visible in the rendered page should carry the same weight as visible links.
Return 404 or Noindex for Empty Pages
Google prefers you to return a 404 status or add a noindex for empty pages, like category pages with no items listed, even if temporary.
Use Last Modified in Sitemaps for Updated Content
The best way to get pages re-crawled which have updated data is to submit in a Sitemap with the last modified date.
Google Measures Sitemap Trust
Google has a trust rating per Sitemap, based on incorrect use of last modified data. Google can learn that the last modified date is providing useful information which increases the trust. Otherwise it will start to ignore the last modified dates.
Last Modified Header used for 304
Last Modified Header is taken into account when using a 304 status code in response to a request which contains an if-modified-since in the request headers.
Avoid Changing URLs
Changing URLs is best avoided as Google has to relearn all the links and context of pages. He admits Google is not perfect at handling these changes which can take a few months to settle down, and recommends planning URLs for the long term.
Re-use Old URLs for Updated Content
For pages which are updated annually, or when a new product model is released, it makes more sense to keep the same URL and update the content, otherwise you may see the old page ranking instead of the new one as it has better ranking signals. If you need to keep the old content, you can republish it on a new archive URL.
Crawl Errors Priority Metric includes Mixture of Signals
The priority metric for crawl errors in search console is a mixture of pages being returned in search results, included in Sitemaps, and if it has internal links. The higher the priority are the ones Google thinks might have content which Google wants to index.
404 Content Isn't Seen by Google
Google doesn’t look at the content of a 404 page.
Full Titles are Indexed and Re-written in SERPs
Google looks at the entire title tag, but only displays a rewritten title in search results which they think is relevant and fits into the space.
Noindex Pages are Indexed but Suppressed from SERPS
Noindex pages are still in the index, they are just suppressed from appearing in search results.
Don't Use Noindex on Canonicalised Pages
Don’t use a Noindex on canonicalised pages, because if Google accidentally picks this as the canonical, nothing will show up in search results.
Background Images are Not Indexed
Images as Div background images will not be indexed in Google Images.
Event Based Interstitials are Not OK