Understanding the Critical Rendering Path
Follow HTML, CSS, and JavaScript through the browser's critical rendering path, then find the resources delaying the first useful render.
Articles
Performance, page 3 of 3
Website performance starts with measuring the experience people actually receive, not chasing a Lighthouse score in isolation. These articles look at rendering behaviour and production bottlenecks, then at the engineering decisions that stop the same regression returning with the next feature or content release.
Understanding the Critical Rendering Path. 
Optimising HTML Markup for SEO. Optimising HTML Markup for SEO
Optimise HTML markup for SEO and accessibility with semantic elements, heading structure, alt text, clean code, anchor text, and crawler‑friendly structure.