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6.2.3. Background Positioning

Thanks to background-repeat, it's possible to place a large image in the background of a document, and then keep it from repeating. Let's add to that and actually change the image's position in the background.


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.1.3. 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 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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Applies to

all elements

WARNING

Percentage values refer to the width of the parent element.

border.

This behavior can be altered by assigning padding to the inlineelement, which will push the borders away from the text itself (shownin Figure 8-58):

SPAN {border: 1px dashed black; padding: 4pt;}
Figure 8-58

Figure 8-58. Inline padding and line-box layout

Note that this padding does not alter the actual shape of thecontent-height, and so will not affect the height of the inline box700. Figure 5-11 shows us the visual result of all this.

Figure 5-11

Figure 5-11. Greater weight will usually confer visual boldness

Let's take this all one step further, and add two more rules, plus some markup, to illustrate how all this works (see Figure 5-12 for the results):

/*   assume only two faces for this example: 'Regular' and 'Bold'   */
P {font-weight: 100;}   /* looks the same as 'normal' text */
P SPAN {font-weight: 400;}   /* so does this */overall, no significant changes in the document's presentation.
We can be quite pleased with the results -- and better still,
management will never notice the difference.

The advantages of the new design are twofold: the ability to change colors and fonts by editing a small number of styles instead of a bunch of FONT tags and a reduction in size of the HTML source itself. In a case like this, a page's size can shrink by several kilobytes -- and in cases where a heavily