Rich Snippets Need to Be Correct, Relevant, and on Quality Pages
In order for rich snippets to be displayed in organic search results, they need to be implemented correctly, relevant to the content and on quality pages.
Crawl Errors are not a Quality Metric
Google considers crawl errors to be technical response, and aren’t considered a quality metric which would impact rankings.
Rich Snippets Won’t be Displayed for Low Quality Pages
Structured markup has to be technially correct, and they are accepted from a policy, and also meet quality criteria to be displayed. If you do a site: command for a URL, and can see the markup appearing, but it doesn’t appear for regular searches, it means the markup has been implemented successfully but the page does not meet the quality criteria.
Valid HTML Isn’t a Ranking Factor
Vaild HTML isn’t a ranking factor. If it works in the browser, and Google can understand the content then it’s OK.
Category Pages Require Unique Content
For category listing pages the pages shouldn’t be completely automated, and should have some unique content, but the page quality is the most important thing.
Reconsideration Requests Don’t Work for Algorithmic Penalties
Reconsideration requests can’t be made for algorithmic penalties like Panda and Penguin. You need to do is disavow the links, or fix the quality issues for the penalty to be lifted in time.
Click Behaviour is Used to Improve Google’s algorithm
The interaction with search results is used to measure search results quality. The more clicking around, the worse the search results page. John says it’s not calculated per query, but it used to assess their different algorithms over large numbers of searches.