HTML is how Web pages are structured. CSS is how Web pages are designed. This book deals primarily with how to use CSS to add a visual layer to the HTML structure of your Web pages. CSS is a style sheet language; that is, it is not a programming language. Instead, it’s code that tells a device (usually a Web browser) how the content in a file should be displayed. CSS is meant to be easily understood by anyone, not just “computer people.” Its syntax is straightforward, basically consisting of rules that tell an element on the screen how it should appear.

The interpretation by the browser’s rendering engine is where your headaches begin. The W3C has gone to great lengths to create specifications by which browser developers should render the Web code. Nonetheless, bugs, omissions, and misinterpretations still creep in, meaning that no two browsers will render a Web page in exactly the same way. For the most part, these differences go unnoticed by most users, but occasionally the differences are glaring and require that you do some extra work to get the page to look right with the broadest spectrum of browsers.

CSS and HTML When HTML was first created, style properties were defined directly in the code. However, rather than just adding more and more tags to HTML, the W3C introduced Cascading Style Sheets to fill the design void in straight HTML, allowing the Web to become semantic in structure. For example. In HTML, the strong tag does one thing and one thing only: It makes text “stronger,” usually by making it bolder. However, using CSS, you can “redefine” the tag so that it not only makes text bolder, but also displays text in all caps and in a particular font to add more emphasis.

Text it is the best system that humans have ever devised for recording complex thoughts. Many people think of text as simply a way to record words, but typography adds a voice to the meaning of the words. Typography affects how text appears by controlling not only the shapes and sizes of the letters used (the font), but also the spaces between letters, words, lines, and paragraphs. Unfortunately, many of the challenges of typography on the Web have come about as a result of a need to circumvent the limitations of the medium.

CSS level 1 (CSS1) The W3C released the first official version of CSS in 1996. This early version included the core capabilities associated with CSS, such as the ability to format text, set fonts, and set margins. Netscape 4 and Internet Explorer 3 and 4 support Level 1. Web designers needed a way to position elements on the screen precisely. CSS1 was already released, and CSS Level 2 was still in the future, so the W3C released a stopgap solution: CSS-Positioning. This standard proposed that the parties concerned could debate for awhile before the CSS-P standard became official.