Cascading style sheets (CSS) are the modern standard for website presentation. When combined with a structural markup language such as HTML, XHTML, or XML (though not limited to these), cascading style sheets provide Internet browsers with the information that enables them to present all the visual aspects of a web document. Cascading style sheets apply things such as borders, spacing between paragraphs, headings or images, control of font faces or font colors, background colors and images, textual effects such as underlined or strike-through text, layering, positioning, and a number of other presentational effects. CSS controls the presentational aspects of a web page's design, whereas HTML, XHTML, or XML controls the structure of a web page, which means little more than determining that certain text is a heading, other text is a paragraph, still other text is a list of hyperlinks, and so on. CSS provides enhanced and precise visual rendering; markup languages such as HTML provide meaning and structure.
"Beginning CSS: Cascading Style Sheets for Web Design, Second Edition" covers all the details required to combine CSS with HTML, XHTML, or XML to create rich, aesthetically powerful designs. Throughout the book, you'll focus on combining CSS with XHTML specifically because XHTML is the standard hailed by Internet standards bodies as the successor to HTML and the present and future of website design. CSS and XHTML allow a web document to be presented with less code, resulting in a significantly smaller file size and greatly increased ease of maintenance. CSS also enables the presentation of a web document to be centralized, which allows for the look and feel of an entire website to be written and centralized in one or a few simple documents, which makes updating a website a breeze. With only a few simple edits to a single document, the look and feel of an entire website can be completely changed.