Tutorials
Short, focused articles on one idea at a time. Filter by level or type, or search for a topic.
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Type, class and ID selectors
Target elements by type, class and ID, group selectors, and why classes are usually the right choice.
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The cascade, specificity and inheritance
How browsers decide which rule wins, calculating specificity, inherited properties, and why to avoid !important.
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Colours in CSS: hex, rgb, hsl and oklch
Every way to write colour in CSS, transparency, and why oklch gives more predictable palettes.
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CSS units: px, em, rem, %, vw and vh
Absolute and relative units, when to use each, and why rem is the usual choice for type.
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The box model: content, padding, border and margin
How every element is a box, how its size is calculated, and margin collapsing.
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box-sizing and controlling element size
border-box versus content-box, width and height, min and max sizes, and the common reset.
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Display: block, inline and inline-block
How display changes layout behaviour, and a first look at flex and grid values.