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Appendix A. CSS Resources

Contents:

General Information
Tips, Pointers, and Other Practical Advice
Online Communities
Bug Reporting

There are a number of very good CSS-related resources available on the Web. Here are some of them.

A.1. General Information

These resources provide a good overview of what's happening in the world of CSS or otherwise provide you with a broad look at CSS.

A.1.1. CSS Recommendations

http://www.w3.org/TR/REC-CSS1

http://www.w3.org/TR/REC-CSS2

When all else fails, you can always use the source, Luke. The specifications contain, albeit in a somewhat terse and not always easily decipherable form, the complete description of how conforming user agents should handle CSS. They also contain a complete CSS parsing grammar and forward-compatible parsing rules, both of which are invaluable to the people who write user agents but of minimal interest to almost everyone else.

A.1.2. W3C CSS Activity Page

http://www.w3.org/Style/CSS

This is, officially speaking, the online center of the CSS universe. There are links to the CSS Recommendations, to new ideas under consideration, and to other sites about CSS. There are links to historical style sheet proposals, to information about current usage and implementations of CSS, and more. There are also lists of books about CSS, news of new CSS tools, and many other useful bits of information.

A.1.3. W3C CSS Test Suite

http://www.w3.org/Style/CSS/Test/

This presents a fairly complete set of pages designed to test any CSS implementation. Each page of the suite tests various aspects of CSS properties, one property per page. The tests were largely developed by the author of this book, Håkon Lie (Opera Software), and Tim

Figure 6-22

Figure 6-22. Applying a background image in HTML

This effect can be duplicated in CSS, but CSS contains a great dealmore than simple tiling of background images. We'll start withthe basics and then work our way up.

The default value of none means about whatyou'd expect: no image is placed in the background. If you wanta background image, then you need only give this property aURL value: Boland (NIST), with many contributions from the CSS community and even the browser vendors themselves. If you're wondering how good your browser is at handling CSS1, this is the place to find out. As of this writing, the Test Suite covers only CSS1, but a CSS2 Test Suite is expected in the near future.

A.1.4. Error Checkers

You can save a lot of time and effort simply by running your CSS through a validity checker. This is particularly recommended if you're thinking about asking for help online, because if your CSS contains errors, the first thing the experts will tell you to do is to use a validator. May as well get into the practice first.

A.1.4.1. W3C CSS Validator

http://jigsaw.w3.org/css-validator/

If you're having trouble getting your style sheets to work, it might be the result of a typographical error, or some other basic error that is difficult to diagnose. You could spend a long time combing through your styles, exhaustively checking each rule for correctness -- and that's a good exercise, of course -- but you could also have a program do it for you, and simply tell you if it found any errors. The W3C CSS Validator will do exactly that. You can supply it with the URL of a style sheet or document containing styles, or simply paste a block of styles into an input field, and let the validator tell you if your problems are the result of a misspelled color name (or something similar). The chief drawback, for most people, is the technical nature of its reporting. Unless you're already familiar with HTML and CSS, the results you get back may be somewhat confusing.

A.1.4.2. WDG CSScheck

http://www.htmlhelp.com/tools/csscheck/

Similar in nature to the W3C's validator, CSScheck offers much friendlier error messages, which makes it more useful to the beginning author. In addition to indicating the severity of the error with whimsical icons (American-style traffic signals, at last check), CSScheck provides a message detailing each problem, as well as the reason it is a problem. It is possible to learn a great deal about good document authoring practices simply by running a few style sheets through CSScheck and carefully reading its responses.



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effect.

Nonetheless, if you leave out this statement, every version ofNavigator 4.x will not extend the background color throughout theentire content box but will only place it behind the element'stext.

11.2.6. The Incredible Shrinking Text!

discussed in detail in the next chapter.)

Finally, it's possible to set a percentage value formargin. The details of this type of value will bediscussed in a later section.

7.3.1. Length Values and Margins

As statedbefore, any length value can be used in setting the margins of an

HTML:lang(de) {color: black; background: yellow;}

Thus would all HTML documents marked as German be shown as black texton a yellow background. This marking could be made with thelang attribute, in a META tagin the document's head, or even as a value in thedocument's HTTP headers. This is somewhat similar to the|= attribute selector discussed in the previoussection, but it is a little more general.

the browser should take the absolute maximum of the negative margins and subtract that from the maximum of any positive margins.

In the case where there are only two margins to be collapsed, one positive and the other negative, the situation is handled in a fairly simple manner. The absolute value of the negative margin is subtracted from the positive margin -- or, to put it another way, the negative is added to the positive -- and the resulting value is the distance between the elements.

Of course, when an element is floated, other content "flowsaround" it. This is familiar behavior with floated images, butthe same is true if you float a paragraph, for example. In Figure 7-64, we can see this effect (a margin has beenadded to make the situation more clear):

P.aside {float: left; width: 5em; margin: 1em;}
Figure 7-64

Figure 7-64. A floating paragraph

One of the first interesting things to