HTML and CSS Reference
grown and evolved far beyond the simple text documents it began with, carrying other types of information
through the same channels: images, video, audio, and fully immersive interactive experiences. But at its
core, the Web is fundamentally a text-based medium, and that text is usually encoded in HTML (more on
that in a minute).
Many different devices can access the Web: desktop and laptop computers, tablets and PDAs, mobile
phones, game consoles, and even some household appliances. Whatever the device, it in turn operates
software that interprets HTML. These programs are technically known as user-agents , but the more
familiar term is web browsers . A web browser is specifically a program intended to visually render web
documents, whereas some user-agents interpret HTML but don't display it.
In this topic we'll generally use the word browser to mean any user-agent capable of handling and
rendering HTML documents, and we may use the term graphical browser when we're specifically referring
to one that renders the document in a visually enhanced format, in full color, and with styled text and
images. It's important to make this distinction because some web browsers are not graphical and only
render plain, unstyled text without any images.
A browser or user-agent is also known as a client , because it is the thing requesting and receiving service.
The computer that serves data to the client is called, not surprisingly, a server . The Internet is riddled with
servers, all storing and processing data and delivering it in response to client requests. The client and the
server are two ends of the chain, connected to each other through the Internet.
What Is HTML?
The World Wide Web originated as a purely textual medium, built upon the written word. Pictures were
soon added to the mix, and eventually sound, animation, and video made the Web the rich multimedia
tapestry it is today. But the overwhelming bulk of Web content still takes the form of written text, and that's
not likely to change any time soon. Most of the time you spend surfing the Web is probably spent reading.
The Web, for all its multimedia richness, is still essentially a textual medium. It's a weave of documents,
cross-referenced and interconnected by the humble hyperlink , wherein a bit of text in one document is
linked directly to another document somewhere else on the Web. And just like that, what would otherwise
be ordinary text becomes the much more exciting and dynamic hypertext , and hypertext needs to be
encoded in a whole new language: HyperText Markup Language (HTML).
HTML is the computer coding language that describes the structure of a web page. It converts ordinary
text into active text for display and use on the Web, and also gives plain, unstructured text the sort of
structure human beings rely on to read it. As you read this topic, you're looking for visual cues to help you
organize the words into smaller portions that you can process and comprehend. You recognize the
significance of things like punctuation, capitalization, spacing, and font sizes. You know just by looking at it
that this paragraph ends after this sentence.