WebAIM conducted an accessibility study of 1,000,000 website homepages. The analysis captured 168 million datapoints and took 66.2 days of cumulative computer processing time. The results are available here and show that the most prevalent WCAG error is low contrast on the page.
I'm a bit late to the CSS3 party here but CSS Tricks have a great visual tutorial on CSS Flexbox and the various layout options available in flexbox. Don't forget to use CanIUse to check browser support though, and here's a handy CSS prefix generator for that cross-browser support (and see some extra steps are here for Safari).
Instant.page is a 1kb library that you can add to your site which pre-loads the next page before a user clicks on a link. The code tests the hover time over a link, and only beings the pre-load when the hover time is over 65ms.
Gajus Kuizinas has an interesting post over on Medium Programming about the lessons learned in scaling a Postgres database to 1.2bn records per month, including the different hosting options and data management and indexing techniques.
HT to the Syntax podcast for mentioning DevDocs.io, a website that has all the docs for every programming language in one place. It is also a progressive web application, which means you can cache the docs for offline reading!