The Slotted Counter Pattern
Optimizations
Powerful Image Optimization Tools — Smashing Magazine
Image Optimization guide for SEO experts and webmasters
WebPageTest - Website Performance and Optimization Test
The Humble Element And Core Web Vitals — Smashing Magazine
Front-End-Performance-Checklist
katiefenn/parker
CSS Analytics - Project Wallace
Yellow Lab Tools - Page Speed audit
Cssstats