web-platform

A small surface anchored to the control that opened it, holding content or controls of its own, and dismissed by clicking away or pressing Escape.

A CSS mechanism that tethers one element to another, sizing and placing it against its anchor and trying fallback positions when the default one would overflow.

A rule that responds to the size of a component's own container rather than the viewport, so one component adapts anywhere it is placed.

The box an element's percentages and offsets are measured against, which is not always its parent and changes with how the element is positioned.

The native masonry mechanism in CSS grid, where one axis keeps strict tracks and the other lets items stack into whichever lane has room.

Building layouts from what the content needs, using grid, flexbox and intrinsic sizing together, instead of imposing a fixed column skeleton.

Layout properties named by flow direction (inline start, block end) rather than by screen edge, so a layout mirrors itself in other writing modes.

Naming regions of a grid and drawing the layout as rows of those names, so items are placed by name instead of by line number.

How a picture or video is resized inside a box whose shape it does not match: stretched to fill, letterboxed to fit whole, or cropped to cover every edge.

Where content is cut to continue in the next fragment, a printed page, a column or a region, plus the rules that decide where the cut may fall.

A grid that decides its own column count from a minimum item width, so the same one line rule works at every screen size without a single breakpoint.

Snap positions declared on a scroll container so scrolling settles on a chosen item edge instead of stopping wherever momentum runs out.

A self contained depth ordering created by certain properties, inside which z-index only competes locally and can never escape to the level above.

A nested grid that borrows its parent's tracks instead of defining its own, so contents of separate children still line up with each other.

The layer above everything else in a document where fullscreen elements, modal dialogs and popovers render, escaping every ancestor's clipping and stacking order.

The visible rectangle of a page inside the browser window, excluding the browser's own bars, and the unit basis for vh and vw.

The pass where script attaches behaviour to server-rendered HTML, turning a page that is already painted and readable into one that answers input.

A link or button that shows more when a reader shows interest in it, by hovering, focusing or long pressing, with no click and no script deciding what interest means.

A button that names the element it acts on and what to do to it, in markup, so opening a dialog or toggling a popover needs no script at all.

The rules that decide what a page becomes on paper: navigation dropped, link targets spelled out, backgrounds abandoned, and the content given page margins.

Fetching, or fully rendering, a page before the reader asks for it, on a guess about where they go next, so the navigation is already done when the click lands.

A stray click the browser emits after a touch has already been handled, landing on whatever moved under the finger in the meantime.

Working out which element sits under a pointer, which decides who receives the event when shapes overlap or transparent areas are in the way.

Closing a transient surface by clicking outside it or pressing Escape, without a dedicated close control being used.

Redirecting all events for one pointer to a chosen element, so a drag keeps reaching the control it started on even when it wanders off.

Hiding the cursor and reading only its movement deltas, so input keeps flowing past the edges of the screen instead of stopping at them.

Keeping the reader's position fixed when content loads or resizes above it, by adjusting scroll offset so the visible text does not jump.

When an inner scroller reaches its end and the gesture continues, the scroll passes to the page behind it unless that handoff is blocked.

Composing an animation on top of whatever is already animating the same property instead of replacing it, so a second nudge adds to the first rather than restarting it.

An animation limited to properties the compositor can handle alone, usually transform and opacity, so it keeps running even when the main thread is busy.

The four-control-point curve that describes how a value moves between its start and end, the default way CSS spells an easing.

The motion an element plays as it arrives, running from a starting style that only exists before the element was ever rendered.

The motion an element plays on its way out, which requires deferring its removal from the layout until the animation has finished.

Whether an animation's first or last keyframe styles apply outside its running window, which decides if an element snaps back when it finishes or stays where it landed.

A technique that measures an element's first and last positions, inverts the difference with a transform, then plays it off, so layout changes animate cheaply.

Animating a container between collapsed and its content's natural size, long impossible because height auto did not interpolate and now opened up by interpolate-size and calc-size().

The rule that produces the intermediate values between two endpoints, which is why some properties can animate smoothly and others can only switch.

A point in an animation where a value is pinned, with the frames between generated by interpolating from one pinned point to the next.

An easing written as a list of sampled stops rather than a curve, which lets CSS express springs and bounces that no cubic bezier can describe.

A defined path an element travels along, with its distance and rotation along that path animated instead of its x and y positions.

Motion that covers a navigation between two whole pages or routes, replacing the hard cut a document load would otherwise produce.

An animation whose progress is bound to scroll position rather than to time, so scrolling back rewinds it exactly.

Animating a programmatic jump so the page travels to its destination instead of cutting there, which keeps an anchor link or a back-to-top button from losing the reader's place.

A scroll timeline measured by one element's passage through the scrollport, with named ranges for entering, being contained, covering, and exiting.

An animated change between two states of a page, where the browser photographs before and after and interpolates the elements the two have in common.

Text mixing a right-to-left script with left-to-right runs such as numbers or Latin words, where each run keeps its own direction.

A CSS length equal to the advance width of the digit zero in the current font, used to set column widths in characters rather than pixels.

A font whose glyphs carry their own colors, gradients, or layers, with a palette the page can override rather than a single ink.

A relative unit equal to the current font size, historically the width of the square the letter m was cast on.

Reshaping a fallback font's size and vertical metrics in CSS so it occupies the same space as the web font and the swap shifts nothing.

The ordered list of typefaces a rule names, each tried in turn until one is available, ending in a generic family.

Shipping only the characters a page actually needs, cutting the font file down and letting the browser fetch ranges on demand.

The empty space a browser splits evenly above and below a line of text when line height exceeds the font's own height, which is why text boxes never sit flush.

Cutting a block of text off after a fixed number of lines, with an ellipsis at the end of the last one.

A space that renders normally but forbids a line break, gluing two words together so they never end up on separate lines.

Optional glyph substitutions and spacing rules packed inside a font file, addressed by four-letter tags and switched on from CSS.

Small guide text set beside or above a run of base text, most often to give the pronunciation of East Asian characters.

An invisible character placed inside a word that marks where a hyphen may appear if the word has to break, and stays hidden otherwise.

Choosing line breaks so a short block of text has lines of roughly equal length instead of a long first line and a stub second one.

Cutting the leftover space above and below a line of text so the box hugs the cap height and baseline instead of the font's full ascent and descent.

Setting lines to run top to bottom in columns rather than left to right, as traditional Chinese, Japanese, and Korean typography does.

A font file downloaded by the page rather than taken from the reader's device, declared in CSS and delivered like any other asset.

Whether a long unbroken string is allowed to split mid-word rather than overflow its container, and where that split may happen.

An invisible character that takes no width and adds a legal break point, letting a long string wrap without showing a hyphen.

A formula for combining a layer's colour with the colour behind it, such as multiply or screen or overlay, instead of simply covering it.

The rule for what happens between two colours in a gradient or transition, including which space the blend runs in and which way around the hue wheel it travels.

The declaration that a page or element supports light or dark rendering, which also tells the browser which palette to use for scrollbars and form controls.

A colour pinned at a position along a gradient, with an optional hint between two stops that moves the halfway point of the transition off centre.

A CSS function that blends two colours by a chosen percentage in a chosen colour space, so hover and disabled variants are derived rather than hand-picked.

A gradient whose colours sweep around a centre point like a clock hand rather than along a line, the shape behind pie charts, colour wheels and progress rings.

A CSS keyword meaning the element's own text colour, letting borders, icons and fills inherit whatever colour the surrounding text happens to be.

An operating system mode that replaces a page's palette with a small user-chosen set of system colours, overriding almost everything an author specified.

A colour written as a hash followed by three, four, six or eight hexadecimal digits, the notation most handoffs still speak even when the source is OKLCH.

A CSS function that takes two colours and returns the one matching the page's current colour scheme, collapsing a theme's light and dark values into one declaration.

One of the CSS keywords such as tomato or rebeccapurple that map to fixed sRGB values, a fossil vocabulary still useful for prototypes and debugging.

A colour notation of lightness, chroma and hue built on Oklab, where changing the hue leaves the perceived lightness alone and equal steps look equal.

How much of what is behind an element shows through it, applied to the whole element and its children at once rather than to a single colour value.

CSS notation that builds a new colour from an existing one by naming an origin colour with from and then adjusting individual channels.

The thumb and track colours of a scrollbar, which a page can set explicitly or leave to the declared colour scheme so the browser draws its own dark variant.

The default colour space of the web, the one hex codes and plain rgb() values live in, and the baseline every wider gamut is described relative to.

A CSS keyword such as Canvas, CanvasText or LinkText that resolves to a colour chosen by the operating system rather than by the page.

Colour beyond what sRGB can express, addressed in CSS through spaces such as display-p3 and rec2020 and shown only on displays that reach that far.

The parallel tree a browser derives from the DOM, holding the role, name, state, and value that assistive technology actually reads.

A proposed API for speaking a message directly to assistive technology, without the live region trick of mutating hidden text and hoping the timing works out.

An attribute that removes an element and its whole subtree from the accessibility tree while leaving it visible on screen.

A shadow root option that forwards focus from the host into the first focusable element inside it, so clicking the padding of a custom element does not leave focus nowhere.

A focus style shown only when focus arrived by keyboard or another non-pointer route, so a mouse click does not leave a ring behind.

A user preference for more contrast than a theme's default, honoured by strengthening borders, text, and state colours rather than by shifting hues.

A state that removes a subtree from focus order, hit testing, and the accessibility tree at once, used to seal the background behind a dialog.

A browser view that throws away your layout and rebuilds the article as plain text the reader can restyle, which is a verdict on how readable the original was.

A CSS property that repoints reading and tab order at the visual arrangement of a flex or grid container, instead of leaving both stuck in source order.

A user preference asking interfaces to cut non-essential animation, honoured by shortening, cross fading, or removing movement rather than by doing nothing.

Reaching for the element that already means what you mean, so name, role, keyboard behaviour, and platform conventions arrive for free instead of being rebuilt.