See also, The CSS Zen Garden
The CSS Zen Garden invites you to relax and meditate on the important lessons of the masters. Begin to see with clarity. Learn to use the time-honored techniques in new and invigorating fashion. Become one with the web.
Lighthouse is an open-source, automated tool for improving the performance, quality, and correctness of your web apps.
When auditing a page, Lighthouse runs a barrage of tests against the page, and then generates a report on how well the page did. From here you can use the failing tests as indicators on what you can do to improve your app.
Get it at Chrome Web Store
Or check out it’s home page
Here’s some feedback from Lighthouse on this here site: