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HTML/CSSIntermediate#css#layout-puzzle
HTML/CSSAdvanced#css#performance
What other CSS performance best practices should you follow?
Minimize deeply nested/expensive selectors, avoid layout thrashing by batching style reads/writes, use will-change sparingly for known animations, lazy-load non-critical CSS, minify and compress stylesheets, and remove unused CSS with tools like PurgeCSS.
Example
/* Avoid expensive universal + descendant chains */
/* bad */
body div ul li a span { color: red; }
/* better: use a single class */
.link-text { color: red; }