Web-Design on emsenn.net

accessibility

Sun, 01 Mar 2026 00:00:00 +0000

Accessibility (often abbreviated a11y) in web design means ensuring that people with disabilities can perceive, understand, navigate, and interact with web content. The term encompasses a wide range of conditions — visual, auditory, motor, cognitive, neurological — and a corresponding range of assistive technologies: screen readers, magnifiers, voice control, switch devices, Braille displays.

Accessibility is grounded in the social model of disability, which locates the barrier not in the person but in the environment. A website that requires a mouse to operate disables anyone who cannot use a mouse. A video without captions disables anyone who cannot hear. The problem is in the design, not in the user.

Accessibility and Universal Design

Sun, 01 Mar 2026 00:00:00 +0000

¶What this lesson covers

What web accessibility means, why it matters, the standards that guide it, and the design principles that make web content usable by people across the full range of human ability and circumstance.

¶Prerequisites

Document Structure and Semantic HTML.

¶What accessibility means

Web accessibility means that people with disabilities can perceive, understand, navigate, and interact with web content. The term covers a wide range of conditions — visual, auditory, motor, cognitive, neurological — and an equally wide range of assistive technologies: screen readers, magnifiers, voice control, switch devices, eye trackers, Braille displays.

Document Structure and Semantic HTML

Sun, 01 Mar 2026 00:00:00 +0000

¶What this lesson covers

How HTML gives structure and meaning to documents, why that structure matters, and how the choice of markup shapes what a document can communicate.

¶Prerequisites

Familiarity with web pages as a reader. No prior knowledge of HTML is assumed.

¶Documents before the web

Before hypertext, most documents were designed for a single rendering: a printed page. Structure — headings, paragraphs, lists, emphasis — was conveyed through visual formatting. A heading was a heading because it was set in a larger typeface, not because the document declared it to be one.

linked data

Sun, 01 Mar 2026 00:00:00 +0000

Linked data is a set of practices for publishing structured data on the web so that it can be interlinked with data from other sources and become more useful through those connections. The term and principles were articulated by Berners-Lee in 2006, building on the W3C’s Resource Description Framework (RDF) and the broader vision of the semantic web.

The four principles of linked data are:

Use URIs (Uniform Resource Identifiers) to name things.
Use HTTP URIs so those names can be looked up.
Provide useful information (using standards like RDF) when someone looks up a URI.
Include links to other URIs so that people and machines can discover related things.

Linked data extends the web’s architecture of hyperlinked documents to hyperlinked data. Where a hyperlink connects one page to another without specifying the nature of the connection, linked data triples connect entities through typed relationships: a person authored a book, a city is located in a country, a chemical has property solubility.

responsive design

Sun, 01 Mar 2026 00:00:00 +0000

Responsive design is an approach to web design in which a page’s layout and presentation adapt to the size, resolution, and capabilities of the device displaying it. Rather than building separate versions of a site for desktop, tablet, and phone, a single HTML document uses flexible layouts and CSS media queries to rearrange itself for each context.

The term was introduced by Ethan Marcotte in a 2010 article for A List Apart and expanded in his book Responsive Web Design [@marcotte_ResponsiveWebDesign_2011]. Marcotte identified three technical ingredients: fluid grids (layouts sized in proportions rather than fixed pixels), flexible images (images that scale with their container), and CSS media queries (rules that apply only when the display meets certain conditions, such as width or orientation).

semantic HTML

Sun, 01 Mar 2026 00:00:00 +0000

Semantic HTML is the practice of choosing HTML elements based on the meaning they convey rather than the visual appearance they produce. A <nav> element declares that its contents are navigation links; an <article> declares a self-contained piece of content; a <header> marks introductory material. These elements communicate structure to browsers, screen readers, search engines, and any other software that processes the document.

The alternative — using generic elements like <div> and <span> for everything and relying on CSS classes for visual differentiation — produces documents that look correct to sighted users but carry no machine-readable structure. Screen readers cannot announce what role a section plays; search engines cannot distinguish primary content from navigation; automated tools cannot extract the document’s outline.

The Semantic Web and Linked Data

Sun, 01 Mar 2026 00:00:00 +0000

¶What this lesson covers

What the semantic web is, how linked data works, the standards that underlie it, and why making information machine-readable matters for knowledge systems.

¶Prerequisites

Document Structure and Semantic HTML. Familiarity with information architecture concepts is helpful.

¶The web of documents and the web of data

The World Wide Web that most people use is a web of documents: HTML pages linked to one another by hyperlinks. A person can follow links, read pages, and synthesize information. But the links between pages are untyped — they say “this page connects to that page,” not how or why. The meaning of each page lives in its natural-language text, accessible to humans but opaque to machines.