What is CSS?

• CSS stands for Cascading Style Sheets
• CSS describes how HTML elements are to be displayed on screen, paper, or in other media
• CSS saves a lot of work. It can control the layout of multiple web pages all at once

A CSS rule consists of a selector and a declaration block.

• The selector points to the HTML element you want to style.
• The declaration block contains one or more declarations separated by semicolons.
• Each declaration includes a CSS property name and a value, separated by a colon.
• Multiple CSS declarations are separated with semicolons, and declaration blocks are surrounded by curly braces.

In this example all p elements will be center-aligned, with a red text color:

Advanced CSS is a set of tools and techniques that help you create the modern websites that employers and clients are looking for. These skills help you make websites more responsive more easily so, whatever kind or size of device someone is using to view your site, it looks fantastic and works well. No more overlapping images or tiny text!

Advanced CSS also allows you to structure your web pages more efficiently. Yep, that means you can forget floats (!!!) but still position and align elements exactly the way you want and have your content flexibly change size or location just the way you need it to. Or you can use advanced CSS to completely customize a site by styling only certain elements or automatically adapting content.

Not only will advanced CSS skills make it possible for you to build and style the kinds of sites that are most in demand nowadays, but they’ll also let you do it more quickly, easily, and efficiently. You’ll be able to get more done with less code, and the code you do write will be more understandable and organized, so you’ll be able to work better both on your own and on a team.

CSS was first proposed by Håkon Wium Lie on October 10, 1994. At the time, Lie was working with Tim Berners-Lee at CERN. Several other style sheet languages for the web were proposed around the same time, and discussions on public mailing lists and inside World Wide Web Consortium resulted in the first W3C CSS Recommendation (CSS1) being released in 1996. In particular, a proposal by Bert Bos was influential; he became co-author of CSS1, and is regarded as co-creator of CSS.

Style sheets have existed in one form or another since the beginnings of Standard Generalized Markup Language (SGML) in the 1980s, and CSS was developed to provide style sheets for the web. One requirement for a web style sheet language was for style sheets to come from different sources on the web. Therefore, existing style sheet languages like DSSSL and FOSI were not suitable. CSS, on the other hand, let a document's style be influenced by multiple style sheets by way of "cascading" styles.

As HTML grew, it came to encompass a wider variety of stylistic capabilities to meet the demands of web developers. This evolution gave the designer more control over site appearance, at the cost of more complex HTML. Variations in web browser implementations, such as ViolaWWW and WorldWideWeb, made consistent site appearance difficult, and users had less control over how web content was displayed. The browser/editor developed by Tim Berners-Lee had style sheets that were hard-coded into the program. The style sheets could therefore not be linked to documents on the web. Robert Cailliau, also of CERN, wanted to separate the structure from the presentation so that different style sheets could describe different presentation for printing, screen-based presentations, and editors.

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