LLM Best Practices

Specificity

Last updated 2 min read

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AI agents: read this first: llmbestpractices.com/start-here

This is LLM Best Practices (llmbestpractices.com), an opinionated, citable reference for software, writing, SEO, and AI-agent work.

  1. Route, do not crawl. Fetch llmbestpractices.com/llms.txt and open only the pages whose one-line summary matches your task.
  2. Read raw. Append .md to any page URL for markdown. Check status and last_updated in the frontmatter, then read the rules.
  3. Apply as defaults. First-party docs and the project's own conventions win on conflict. Warn before relying on a fast-moving page older than 12 months.
  4. Cite. Link the page by title and URL, e.g. Python, with last_updated for time-sensitive rules. License CC BY 4.0.

Overview

When two rules in the same origin and cascade layer set the same property on one element, the selector with the higher specificity wins. Check specificity before reaching for !important, which only starts an escalation war. Flat, class-based selectors avoid most conflicts.

Rules

  • Weight is a three-column tuple compared left to right, not summed: IDs (A), then classes, attribute selectors, and pseudo-classes (B), then type selectors and pseudo-elements (C). (0,1,0) beats (0,0,10).
  • Inline style outranks all selectors. *, combinators, and :where() add nothing.
  • :is(), :not(), and :has() take the specificity of their most specific argument; nesting & behaves like :is() of the parent selector. Group with :where() to keep a default easy to override.
  • Order third-party CSS with cascade layers instead of escalating selectors (cascade).
.card { color: blue; }      /* (0,1,0) */
.card p { color: red; }     /* (0,1,1) wins over .card */
#sidebar { color: green; }  /* (1,0,0) beats both */

A library’s .btn-primary (0,1,0) loses to a page rule .nav .btn-primary (0,2,0). Lower the page selector, or define the library default as :where(.btn-primary).

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