How HTML and CSS work together, and the three ways to attach styles to a page.
HTML defines structure and meaning, while CSS controls presentation; keeping them separate makes pages easier to maintain, reuse and make accessible. CSS can be applied inline through the style attribute, internally with a <style> element in the head, or externally by linking a stylesheet with <link rel="stylesheet">. External stylesheets are generally preferred because the browser can cache them and share them across pages.
Interviewers commonly ask about specificity and the cascade: when multiple rules target the same element, inline styles beat ids, ids beat classes, and classes beat element selectors, with source order breaking ties and !important overriding the normal rules. Another recurring topic is where stylesheets and scripts belong, since CSS in the head avoids a flash of unstyled content while render-blocking scripts are better deferred with the defer or async attributes.
What you'll walk away knowing