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Frontend & Web Development

CSS

CSS controls the presentation and layout of HTML content, including color, spacing, typography, and responsive behavior.

CSS controls the presentation and layout of HTML content, including color, spacing, typography, and responsive behavior. Good implementations remain semantic, maintainable, and fast across devices and input methods. The concept is closely related to HTML and Design Token.

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HTML

Design Token

Responsive Design

Critical CSS

FAQ

CSS

How does CSS affect page load time?
CSS blocks rendering: the browser shows content only after the relevant stylesheets have loaded. Large or numerous files therefore delay the first visible paint. Delivering critical rules early and removing unused ones shortens that path. Styles that arrive late can also trigger layout shifts.
What typical mistakes occur when writing CSS?
Common problems include overly high specificity, overrides via !important, fixed pixel values instead of relative units, and duplicate rules with slightly different values. The result is a stylesheet nobody dares to touch. Consistent naming conventions, tokens instead of one-off values, and regular removal of unused rules counter this.
Where is the line between HTML and CSS?
HTML provides meaning and structure, while CSS provides appearance. A heading stays a heading no matter how it is styled. Building structure through looks alone, such as a button made from a div, costs accessibility and machine readability. A clean separation makes redesigns possible without reworking content.
When should CSS be added inline, internally, or as an external file?
External stylesheets are the default because browsers cache them and changes happen in one place. Inline styles fit only single, dynamically generated values. An internal style element in the head suits small, page-specific exceptions. The more scattered the rules are, the harder changes become to trace and override.