Building web pages with HTML and CSS

Every page on the web is, at its core, a text document written in HTML. The language works through elements delimited by tags, written in angle brackets, that wrap pieces of content and describe their role: a paragraph, a heading, a hyperlink, an image, a table, or a form field. Most elements have an opening and a closing tag, and elements can be nested inside one another to build a tree-like structure that the browser then renders into the page a reader sees.

Appearance is handled separately by Cascading Style Sheets. Rather than mixing formatting into the markup, CSS lets an author write rules that target elements and set properties such as colour, typeface, margins, and positioning. Because a style sheet can be shared across an entire site, a consistent look is easy to maintain and a single change can update many pages at once. The word “cascading” refers to the way rules from different sources combine and override one another according to defined priorities.

Beyond static structure and style, several technologies add behaviour and modularity. Client-side scripting, written in a language such as JavaScript and combined with HTML and CSS as dynamic HTML, lets a page react to the user. Frames, and in particular inline frames, allow one HTML document to embed another within a region of the page. On the server side, mechanisms such as CGI scripts and ASP generate HTML before it is sent, producing pages tailored to each request. Learning how these pieces fit together is the basis of web design.

Frequently asked questions

What is an HTML tag?

A tag is the markup, written in angle brackets, that begins or ends an HTML element and tells the browser the role of the content it surrounds, such as a heading, paragraph, or link.

What is an inline frame?

An inline frame is an HTML element that embeds one web document inside a region of another, letting a page display separate content within part of its layout.

What is the difference between client-side and server-side technology?

Client-side scripting runs in the browser to change a page after it loads, while server-side technologies such as CGI and ASP build the HTML on the server before sending it to the browser.