Web Accessibility
Definition
Web accessibility describes how well a page works for someone whose sight, hearing, movement or cognition differs from the person who built it. It is measured against the Web Content Accessibility Guidelines, which sort every requirement under four principles: perceivable, operable, understandable and robust. WCAG 2.2 is the current version, published as a W3C Recommendation in October 2023; version 2.1 from 2018 and version 2.0 from 2008 are still the ones most laws name. Each guideline breaks into testable success criteria graded Level A, AA or AAA, and Level AA is what policy and procurement almost always ask for. Accessibility is not a widget you bolt on at the end. It lives in the markup, the colour values, the focus order and the words you choose.
Why It Matters
The World Health Organization puts the number of people living with a significant disability at about 1.3 billion, roughly one in six. WebAIM's annual scan of a million home pages keeps finding detectable WCAG failures on around 95 per cent of them, and the same handful of faults dominate: low contrast text on about four pages in five, missing alt text on more than half, unlabelled form fields on roughly a third. None of those is exotic. Each is an hour of work, and each one locks out a real group of people. In the EU the European Accessibility Act has applied to many consumer-facing digital products and services since 28 June 2025, and in the United States, ADA compliance claims over websites run to thousands of filings a year — that is the general shape of the law, not legal advice.
How It Works
A browser builds two things from your HTML: the DOM it paints on screen, and an accessibility tree it hands to assistive software. Semantic HTML fills that tree for free — a heading arrives as a heading with a level, a button as a button, a nav element as a navigation landmark. Assistive technology then reports each node's name, role, value and state, which is why a control with no accessible name is announced as nothing more than 'button'. Keyboard support comes from the same source: native interactive elements sit in the tab order and respond to Enter or Space with no script at all. Testing has two halves — an automated pass with a tool such as axe or Lighthouse, which catches perhaps a third of the criteria, and a manual pass where you put the mouse down and then listen to the page.
Real-World Example
A designer publishes a one-page portfolio as 'index.html' at rosa-studio.99helpers.site. It looks finished, but the thumbnails carry no alt attribute, the menu is built from styled div elements, and the body text is #999999 grey on white — a ratio of 2.85:1, well under the 4.5:1 minimum. Rewriting the menu as a nav with real anchors, writing alt text for eleven images and darkening the grey to #595959, which measures 7:1, takes about forty minutes. 99helpers serves the corrected file at the same address the moment it is uploaded, so every link already sent to clients keeps working.
Common Mistakes
- ✕Treating accessibility as a final QA pass — by then the layout, the palette and the component structure are fixed, and what would have been small fixes have become rewrites
- ✕Trusting a perfect automated score — tools check only what a machine can check, roughly a third of the success criteria, and none of them can tell a useful alt text from a wrong one
- ✕Adding an overlay widget and calling the site compliant — overlays do not change the underlying markup, and screen reader users report in survey after survey that they switch them off
Related Terms
WCAG
WCAG, the Web Content Accessibility Guidelines, is the W3C standard that defines what accessible web content is. Its success criteria at Levels A, AA and AAA are what accessibility law and procurement point to.
Screen Reader
A screen reader is software that turns what is on screen into speech or braille and gives the user a keyboard interface for moving through it. JAWS, NVDA, VoiceOver, Narrator and TalkBack are the ones in common use.
Semantic HTML
Semantic HTML means using the element that matches the meaning of the content — button, nav, h2, label, table — rather than styling a generic div or span to look the part.
ADA Compliance
ADA compliance refers to meeting the Americans with Disabilities Act as it has been applied to websites and digital services. The statute names no web standard, so the picture is built from regulation and case law rather than from a single document.
Static Site
A static site is a website made of finished files — HTML, CSS, JavaScript, images — that are sent to the browser exactly as they are stored. Nothing is assembled on the server when a visitor arrives.
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