Definitions beginning with A

A/B testing

Method comparing two variants of a page, message or journey to measure which one best achieves a goal.

In practice: compare one hypothesis at a time and decide beforehand what result would justify a change.

Above the fold

The part of a page visible before the first scroll. It should quickly present the topic, value proposition and useful next action.

In practice: Check on a real phone that the topic, benefit and next step are clear before scrolling.

Acceptance criteria

Specific, testable conditions used to decide whether a delivered feature or page meets the agreed need.

In practice: state an observable result, test conditions and the person who accepts it.

Accessibility conformance report

Document reporting a product’s conformance with accessibility criteria and the limitations found.

In practice: Read the report’s scope, method and exceptions before reusing a conformance percentage.

Accessibility tree

A representation exposing information such as element names, roles and states to assistive technology. It depends on browser and markup; visual appearance alone does not establish its contents.

Reference: MDN : Accessibility tree · Source consulted 2026-10-18

In practice: Compare the order and names exposed to assistive technology with the visual page journey.

Accessible description

Information supplementing an element’s accessible name, such as instructions or constraints. It provides context without replacing the name needed to identify the control. Associate help with the correct field and check that it remains available when an error appears. A description should not hide essential instructions.

Reference: W3C WAI · Accessible names and descriptions · Source consulted 2026-10-25

Source consulted : W3C · 2026-10-17

In practice: Use a longer description when context cannot fit in the accessible name alone.

Accessible entrance

Entrance whose relevant access characteristics are clearly described to help plan a visit.

In practice: describe the entrance’s actual features without a vague promise.

Accessible name

Name used by assistive technologies to identify an element, such as a field or button. It should convey purpose and remain consistent with the visible label. Inspect the computed name in the accessibility tree: an icon that makes sense visually can still be unnamed for a screen reader.

Reference: W3C WAI · Accessible names and descriptions · Source consulted 2026-10-25

Source consulted : W3C · 2026-10-17

In practice: check the name actually announced for each button and field with a screen reader.

ACME

Protocol for automating certificate management, including proof of control over the relevant names.

Reference: Let’s Encrypt : Integration Guide

Identify the client, profile and latest renewal result, then inspect the served certificate.

ACME Renewal Information

ACME extension letting an authority suggest a renewal window to its client.

Reference: Let’s Encrypt : Integration Guide

Verify authority and client support, then observe renewal behaviour.

ACME staging environment

Test service for preparing an ACME integration; its certificates are not intended for visitor trust in production.

Reference: Let’s Encrypt : Staging Environment

Separate integration testing from inspection of the production certificate actually presented.

Acquisition

All actions intended to attract new visitors, prospects or customers through search, advertising, content or partnerships.

In practice: connect each channel to useful enquiries, not just visit counts.

Active filter

Criterion currently applied to a result list, such as a region or availability. The interface should explain what restricts the list, allow removal of a criterion and provide a route to broader results. No matches should remain distinguishable from an error or ongoing loading.

Reference: W3C WAI : User notifications · Source consulted 2026-10-18

In practice: combine two filters, remove one using the keyboard and then use browser back. Check the result count, displayed criteria and announcement of changes to assistive technology without moving focus unnecessarily.

Ad blocker

Software or browser extension that blocks some or all advertising and tracking scripts.

In practice: Check that essential content and functions remain available when third-party scripts are blocked.

AEO

Answer Engine Optimization: organizing content to provide direct, precise answers that answer engines can easily reuse.

In practice: Answer a precise question on the page first and connect the answer to verifiable evidence.

Affiliate marketing

Model in which a traffic partner receives payment when a click, lead or sale meets agreed conditions.

In practice: Clearly distinguish editorial recommendation from payment tied to a link.

Agentic commerce

Digital commerce in which an agent can search, compare or prepare a transaction under a person’s control and preferences.

In practice: Check ordering, returns and consent terms before an agent can confirm a purchase.

Agentic Web

Evolution of the Web in which software agents read content and use interfaces or structured tools to complete tasks.

In practice: Describe tasks an agent may complete on the site and stages where a person stays in control.

AI Act

European regulation governing certain AI systems according to risk level, use and the obligations of the organizations involved.

In practice: Identify the actual use and responsible person, then check applicable obligations in the current official text.

AI agent

AI system able to chain steps, use tools and pursue a goal with a degree of autonomy.

In practice: Define allowed actions, human approval points and how to undo an error.

AI citation

Link or reference presented with a generative answer to attribute information to a source that can be checked.

In practice: record the question, date, link and exact wording before counting a citation.

AI crawler

Crawler that visits Web pages for search, indexing, assisted answers or, depending on its stated purpose, training.

In practice: distinguish search crawlers, training crawlers and visits triggered by a person.

AI discoverability

Ability of content to be crawled, understood, retrieved and cited by AI-assisted search or answer systems.

In practice: start with a public, indexable, understandable page, then observe available search surfaces.

AI evaluation

Reproducible protocol measuring the quality, safety, consistency or cost of an AI system on defined cases.

In practice: collect real examples and success criteria before comparing answers.

AI Mode

Google generative search experience that builds an answer and offers links from multiple searches and sources.

In practice: Observe answers and links for specific questions without assuming stable ranking.

AI Overviews

Generative summaries shown by Google Search for some queries, with links to pages used to explore the answer further.

Reference: Google Search Central : AI features

In practice: Track visibility, clicks and visit quality separately when this format appears.

AI readiness

Readiness of data, processes, skills, controls and objectives required for responsible AI use.

In practice: check data quality, answer ownership and evaluation method before choosing a model.

AI red teaming

Adversarial evaluation deliberately searching for failures, misuse, bypasses or harmful effects in an AI system.

Reference: Microsoft Learn · AI red teaming · Source consulted 2026-10-31

In practice: Define prohibited behaviour and realistic scenarios, then record failures and fixes.

AI search

Search combining source retrieval, generative models and a conversational interface to build or refine an answer.

In practice: Publish sourced answers on accessible pages and measure observable visits or mentions.

AI-assisted search

Search features that assemble an answer from multiple sources and may link to supporting pages.

In practice: answer a real question with facts you can check.

Algorithm

Defined sequence of instructions used to solve a problem, process data or produce a result.

In practice: Describe inputs, rule and edge cases before judging the result.

Algorithmic transparency

Information provided about an algorithmic system’s purpose, data, limits, decisions and governance.

In practice: Explain which data and rules influence a decision without publishing a misleadingly simplified account.

Alternative text

Text alternative chosen according to an image’s function in context. Decoration can have an empty alternative; an image carrying information needs a relevant equivalent.

Reference: W3C WAI : Images

Source consulted : W3C · 2026-10-17

In practice: describe what the image adds here, without a keyword list.

AMP

Former accelerated mobile page format initiated by Google. Its use has declined in favor of fast conventional responsive websites.

In practice: Check whether this format still meets a real need and measure the cost of maintaining two versions.

Anchor text

Visible text of a link, helping readers anticipate its destination before opening it. Useful anchor text describes the subject or action in context without piling up keywords. It should remain understandable for someone browsing links with a keyboard or screen reader.

Reference: Google Search Central : Links · Source consulted 2026-10-18

In practice: replace “click here” with a specific destination such as “Collection point opening hours”. Read the page’s links separately: identical labels leading to different destinations can make choosing difficult.

Answer engine

Service designed to provide a concise, sourced answer rather than only a ranked list of links.

In practice: Test several phrasings of a question and check answer sources, not merely their presence.

API

Interface defining how software exchanges data or requests operations. Its contract specifies inputs, responses and errors; knowing an address does not automatically grant access rights. Before integration, distinguish available operation, response format and permission. A technically received response may still contain an error or an incomplete result.

Reference: MDN · API · Source consulted 2026-10-25

Source consulted : MDN · 2026-10-17

In practice: before connecting systems, define exchanged data, possible errors, necessary permissions and ownership on both sides.

API contract

Documented agreement on an API’s inputs, outputs, errors and usage conditions. Defining versions and edge cases helps client software detect an incompatible change.

Reference: OpenAPI Initiative : Specification

Source consulted : OpenAPI Initiative · 2026-10-17

Have the consuming team review a normal and refused case before considering the integration ready.

API-first content

Content structured independently of an interface so it can be distributed consistently to several sites, applications or services.

In practice: Define fields, reuse and editorial ownership before connecting several channels.

ARIA

Roles, states and properties for assistive technologies. ARIA describes an interface; it does not itself add the keyboard behaviour or logic a component requires. Prefer a native HTML element when it meets the need. When adding a role, also test its states and expected interactions.

Reference: W3C WAI · ARIA Authoring Practices · Source consulted 2026-10-25

Source consulted : W3C · 2026-10-17

In practice: start with native HTML; add ARIA only for information missing from its semantics.

ARIA live region

Region whose changes can be announced to assistive technologies without moving focus. Announcement priority should match urgency; excessive announcements can interrupt reading. Reserve urgent announcements for situations that warrant them. Test search results, errors and successive updates with a screen reader.

Reference: MDN · ARIA live regions · Source consulted 2026-10-25

Source consulted : MDN · 2026-10-17

In practice: Announce only meaningful changes and test their frequency to avoid overwhelming speech.

Arrival directions

Text instructions for finding a place’s entrance beyond its address alone.

In practice: test the route from the street to the correct door.

Art direction

Choosing different crops or compositions for different display spaces. HTML picture can offer these variants; changing composition is distinct from selecting a different resolution.

Reference: MDN : Responsive images · Source consulted 2026-10-18

In practice: Choose a different crop only when the subject remains understandable at every size.

Artificial intelligence

Methods allowing computer systems to perform tasks associated with perception, language, prediction, reasoning or decision-making.

In practice: Start with the problem and an evaluation method before choosing a technique.

Asynchronous

Execution in which a program can continue other work while waiting for an operation such as a network response. Responses may arrive in a different order from requests. Loading, errors and outdated responses therefore need handling without blocking the interface.

Reference: MDN : Asynchronous · Source consulted 2026-10-18

In practice: Provide loading, error and cancellation states so people understand what is happening.

Attribution

Method assigning conversion credit across the channels and touchpoints in a journey.

In practice: record each source’s limits before assigning a sale to a single channel.

Audience

Group of people likely to view content, use a service or receive a message.

In practice: describe the intended people’s questions and constraints before choosing messages.

Authentication

Verification of a person’s or system’s claimed identity using appropriate factors. It may need repeating for a sensitive action. It differs from authorisation: recognising an account does not grant access to every object or operation.

Reference: OWASP : Authentication · Source consulted 2026-10-18

In practice: Map sign-up, recovery and revocation before choosing a sign-in method.

Automation

Use of rules or tools to execute repetitive tasks with less manual intervention.

In practice: Start with a repeated task whose exceptions and owner are known.

AVIF

Image format based on AV1 for still images and sequences. It can reduce size, with quality, encoding and compatibility trade-offs to check. Compare versions of the same image at identical dimensions, checking fine detail, transparency and file size. The format alone does not predict savings.

Reference: MDN · Image file types and formats · Source consulted 2026-10-25

Source consulted : MDN · 2026-10-17

In practice: compare appearance, size and compatibility against another format on site images.