Web Design Glossary
Plain-English definitions of 32+ web design and SEO terms — written for founders, not engineers.
A
Above the fold
The portion of a webpage visible without scrolling.
Originally a newspaper term, 'above the fold' refers to the content visible immediately when a page loads, before any scrolling. Critical for first impressions and conversion — primary CTAs, value propositions, and hero imagery typically live here.
Accessibility (a11y)
Designing sites usable by people with disabilities.
Accessibility ensures websites work for users with visual, auditory, motor, or cognitive impairments. WCAG 2.1 AA is the standard most regulators reference. Includes color contrast, keyboard navigation, alt text, semantic HTML, and screen-reader compatibility.
ARIA
Attributes that improve accessibility for screen readers.
Accessible Rich Internet Applications (ARIA) is a set of HTML attributes that make dynamic web content more accessible. Used to label elements, define roles, and indicate states for assistive technology.
B
Bounce rate
Percentage of visitors who leave after one page.
Bounce rate measures single-page sessions. High bounce rates can indicate poor content match, slow loads, or broken UX. Modern analytics (GA4) replaces this with engagement rate, which is often more useful.
Breadcrumbs
Navigation showing user's location in the site hierarchy.
Breadcrumb navigation displays the path from the homepage to the current page. Improves UX, internal linking, and SEO when paired with BreadcrumbList schema.
C
Call to action (CTA)
A prompt directing users to take a specific action.
CTAs are buttons or links designed to drive conversion: 'Get a quote,' 'Sign up,' 'Buy now.' Effective CTAs are visually distinct, action-oriented, and placed at decision moments throughout the page.
CMS (Content Management System)
Software that lets non-developers edit website content.
A CMS like WordPress, Webflow, or Contentful separates content from code, letting marketing teams publish without engineering. Trade-off: more flexibility for editors usually means more complexity for developers.
Conversion rate
Percentage of visitors who complete a desired action.
Conversion rate is the percentage of visitors who complete a goal: form submit, purchase, signup. Average B2B conversion rates land around 2-3%; well-optimized sites hit 5-10%.
Core Web Vitals
Google's three metrics for page experience.
Largest Contentful Paint (LCP, target under 2.5s), Interaction to Next Paint (INP, target under 200ms), and Cumulative Layout Shift (CLS, target under 0.1). Poor scores hurt both UX and search rankings.
CSS
The language that styles HTML pages.
Cascading Style Sheets (CSS) controls colors, layout, typography, and animation on web pages. Modern CSS includes Flexbox, Grid, custom properties, and container queries.
D
Domain name
The human-readable web address (e.g., sitefyd.com).
A domain name is the address users type to reach a site. Registered through a registrar, mapped to a server via DNS. Costs $10-$30/year for common TLDs.
DNS
The system that maps domain names to servers.
Domain Name System (DNS) translates 'sitefyd.com' into the IP address of the server hosting the site. Changes can take minutes to 48 hours to propagate globally.
H
Headless CMS
A CMS that delivers content via API, not pre-rendered pages.
Headless CMSes (Contentful, Sanity, Strapi) store content but leave rendering to your front-end. Useful for multi-channel publishing, modern frameworks, and performance.
Hosting
The server infrastructure that serves your website.
Hosting providers (Vercel, Netlify, Cloudflare, AWS) store your site files and serve them to visitors. Static hosting is fastest and cheapest; dynamic hosting is needed for backend code.
HTML
The markup language that structures web content.
HyperText Markup Language (HTML) defines the structure of a webpage: headings, paragraphs, links, images. Semantic HTML uses meaningful tags for accessibility and SEO.
J
JSON-LD
Structured data format for SEO and rich results.
JavaScript Object Notation for Linked Data (JSON-LD) is the format Google recommends for embedding schema markup. Enables rich results: ratings, FAQs, breadcrumbs, prices in search.
L
Landing page
A focused page designed for a single conversion goal.
Landing pages have one job: convert traffic from a specific source (ad, email, campaign) into a specific action. They strip navigation and focus the eye on the CTA.
LCP (Largest Contentful Paint)
Time until the largest visible element loads.
LCP measures how quickly the largest visible element (usually a hero image or headline) renders. Target under 2.5 seconds on mobile. One of three Core Web Vitals.
Lighthouse
Google's automated tool for auditing site quality.
Lighthouse audits performance, accessibility, SEO, and best practices. Scores 0-100 across each category. Built into Chrome DevTools and PageSpeed Insights.
M
Meta description
The summary shown under your page title in search results.
Meta descriptions are HTML tags summarizing a page's content. Google uses them as the snippet text in search results. Target 150-160 characters, written to drive clicks.
O
Open Graph
Meta tags that control how links preview on social media.
Open Graph tags (og:title, og:description, og:image) control how URLs appear when shared on Facebook, LinkedIn, Slack, and other platforms. Twitter has its own twitter:card variant.
R
Responsive design
Layouts that adapt to any screen size.
Responsive design uses CSS media queries to render the same site appropriately on phones, tablets, and desktops. Mobile-first design starts with the smallest screen and adds complexity for larger ones.
S
Schema markup
Code that helps search engines understand page content.
Schema markup (typically JSON-LD) labels page content as a Recipe, Product, FAQ, etc. Enables rich results in search and improves citations by AI assistants.
Semantic HTML
Using meaningful HTML tags (article, nav, main) for structure.
Semantic HTML uses tags that describe their content (article, section, nav) instead of generic divs. Improves accessibility, SEO, and code readability.
SEO
Optimizing a site to rank in search engines.
Search Engine Optimization combines technical (crawlability, schema, speed), on-page (titles, content, structure), and off-page (backlinks, mentions) work to improve rankings.
Sitemap
An XML file listing all your site's URLs.
Sitemaps help search engines discover and prioritize pages. Submit through Google Search Console and reference in robots.txt. Large sites split into multiple sitemaps with a sitemap-index.
SSL/TLS certificate
Encryption that enables HTTPS.
SSL/TLS certificates encrypt traffic between user and server. Required for HTTPS, trust badges, and most browser features. Free certificates from Let's Encrypt are universal.
Static site
A site served as pre-built HTML files (no backend).
Static sites are pre-rendered to HTML at build time, served directly from CDN. Fast, secure, cheap to host. Modern frameworks (Next.js, Astro, Eleventy) make them powerful.
T
Title tag
The HTML tag containing your page's title (shown in search).
The <title> tag is what appears in browser tabs and as the headline of your search result. Target under 60 characters, primary keyword near the start.
U
UX (User Experience)
How a user feels while interacting with your site.
UX encompasses every aspect of how users interact with a site: layout, navigation, copy, performance, accessibility. Good UX is invisible — bad UX is the only kind users notice.
W
WCAG
Web Content Accessibility Guidelines (the a11y standard).
WCAG 2.1 (with 2.2 emerging) is the global standard for web accessibility. AA conformance is the legal requirement in most jurisdictions. AAA is the gold standard.
Wireframe
A low-fidelity layout sketch made before visual design.
Wireframes show structure without color, typography, or imagery. Used to align stakeholders on layout and content hierarchy before investing in visual design.