Book HomeCascading Style Sheets: The Definitive GuideSearch this book Friday 06th of March 2015 06:26:42 PM

Preface

The subject of this book is, as you might have guessed by the cover, Cascading Style Sheets (CSS). There are two "levels" to CSS; these are referred to as CSS1 and CSS2. The difference between the two is that CSS2 is all of CSS1, plus a lot more. This book attempts to cover all of CSS1, and CSS positioning, which is a part of CSS2. The rest of CSS2 is excluded because, at the time of this writing, nobody had implemented most of it. Rather than cover a lot of theoretical territory, we chose to stick to what was currently usable.

If you are a web designer or document author interested in sophisticated page styling, improved accessibility, and saving time and effort, then this book is for you. All you really need before starting the book is a decent knowledge of HTML 4.0. The better you know HTML, of course, the better prepared you'll be. You will need to know very little else in order to follow this book.

It is important to remember something about web standards and books: the former are continually evolving, while the latter are frozen in time (until the next edition comes out, anyway). In the case of HTML and CSS, there are a great many changes afoot even as these words are being written. The recent formalization of XHTML 1.0 as a full W3C Recommendation, for example, is a major milestone in the evolution of whole story: the borders around an element are also considered to be part of its foreground. Thus, there are two ways to directly affect the foreground color of an element: by using the color property and by setting the border colors using one of a number of border properties. Primarily there is the border-color property, as well as shorthand properties such as border-top, border-right, border-bottom , border-left, and border.

the World Wide Web. There are likely to be even more levels to CSS, further extending the ability to style documents; major web browsers are approaching full CSS1 support, and robust CSS2 implementations can be seen lurking on the horizon. This is an exciting time to be a designer, and learning CSS now will give you a leg up on the future.

0.1. Typographical Conventions

The following typographical conventions are used in this book:

Constant width

is used to indicate code examples, HTML tags and CSS elements.

Constant width italic

is used for replaceables that appear in text.

Italic

is used to introduce new terms and to indicate URLs, filenames, and pathnames.

TIP

indicates a note or tip relating to the nearby text.

WARNING

indicates a warning.



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I will take a break from my normal pragmatic approach to getting you (the programmer) started with using XML and Java and just talk about the high level (design level) benefits of this wonderful combination. A good design is important to a good implementation for any system.

XML is structured

When you create your data using an XML editor (that you can write), you can not only input the content of your data, but also define the structural relationships that exist inside your data. By allowing you to define your own tags and create the proper structural relationships in your information (with a DTD), you can use any XML parser to check the validity and integrity of the data stored in your XML documents. This makes it very easy to validate the structure and content of your information when you use XML. Without XML, you could also provide this validation feature at the expense of developing the code to this yourself. XML is a great time saver because most of the features that are available in XML are used by most programmers when working on most projects.

By using XML and Java, you can quickly create and use information that is properly structured and valid. By using (or creating) DTDs and storing your information in XML documents, you have a cross-platform and language independent data validation mechanism (for free) in all your projects!

and 900, lacking a heavier face, are assigned to the Bold font face. Finally, 600 is assigned to the next-heavier face, which is, of course, the Bold face.

font-weight is inherited, so if you set a paragraph to be bold, then all of its children will inherit that boldness, as we see in Figure 5-9.

P.one {font-weight: bold;}
Figure 5-9

Figure 5-9. Inherited font weight

of the BODY element. Similarly, the first paragraph in the first DIV is italicized because it is the first child of the DIV, even though text preceded it. Only structural elements count for this pseudo-class, so the text before the paragraph doesn't affect the paragraph's status as the first child. However, in the second DIV, the H2 is the first child, so it does not match the rule P:first-child. If the intent is to have the first child of any element be italicized, no matter what element that might be, then you need only leave off

By making the W3C the keeper of the XML standard, it ensures that no one vendor should be able to cause interoperability problems to occur between systems that use the open standard. This should be reassuring to most companies making an investment in this technology, by being vendor neutral, this solution proposes to keep even small companies out of reach of big companies choosing to change the standards on them. For example, if a big company chooses to change the platform at its whim, then most other companies relying on that platform suffer. By keeping all data in XML and using XML in communications protocols, companies can maximize the lifetime of their investment in their products and solutions.

XML is language independent

By being language independent, XML bypasses the requirement to have a standard binary encoding or storage format. Language independence also fosters immense interoperability amongst heterogeneous systems. It is also good for future compatilbilty. For example, if in the future a product needs to be changed in order to deal with a new computing paradigm or network protocol, by keeping XML flowing through the system, addition of a new layer to deal with this change is feasible.

DOM and SAX are open, language-independent set of interfaces