There are a few areas that CSS1 does not address, and therefore are not covered in detail in this book; some of these topics are touched upon in Chapter 10, "CSS2: A Look Ahead". Of course, even a full-blown CSS implementation, covering all of CSS1 and CSS2, would not meet every request from every page designer in the world. It's worth going through some of the boundaries of CSS.
When you get right down to it, CSS1 is not an overly complicated specification. The entire thing can be printed out in less than 100 pages, and it contains about 70 properties. It is still a very sophisticated and subtle engine, but some areas of web design were omitted from CSS1.
In the first place, CSS1 had almost nothing to say about tables. You might think that you can set margins on table cells, for example -- and a web browser might even let you do so -- but margins should not be applied to table cells under any circumstances. CSS2 introduced a new set of properties and behaviors for dealing with tables, but as of this writing, few if any of these are supported.
To a certain degree, the omission of tables from CSS1 says a great deal about the feeling many have that tables should never be used to lay out pages. It is felt that floated and positioned elements should do all of the work tables used to do, and more. Whether this premise can be supported is not a discussion I intend to undertake here.
Yes, that's really all there is to it. One simpleurl value, and you're putting images in forbullets, as you can see in Figure 7-81.
Figure 7-81. Using images as bullets
Of course, you should exercise care in the images you use, as thisexample makes painfully clear (shown in Figure 7-82):
In a similar way, CSS1 contains nothing in the way of positioning. Sure, it's possible to move elements around a little bit, but mostly with negative margins and floating. Everything is, in a sense, relative. CSS2, on the other hand, has three chapters devoted to the visual rendering model, which includes the positioning of elements.
CSS1 makes no provision for downloadable fonts. This leads to a good deal of discussion about how to account for user system configurations and available fonts. CSS2 introduces some font-handling, but even there the issue is not resolved, mostly due to the lack of a widely supported font format. It may be that Scalable Vector Graphics (SVG) will solve some or all of this problem, but it is impossible at this point to say with any certainty.
Finally, there is a lack of media types in CSS1. In other words, CSS1 is primarily a screen-device language, intended to be used to put content onto a computer monitor. There is some thought toward paged media, like printouts, but not much. (Despite this, CSS1 is not a pixel-perfect control mechanism.) In an effort to overcome this limitation, CSS2 introduces media types, which makes it possible to create separate style sheets that are applied to a document depending on its display media. CSS2 also introduces properties and behavior specifically aimed at paged media and aural media.
Sadly, the major drawback to using CSS is that it was so poorly implemented at first. Through a combination of miscommunication, misinterpretation, confusion, and poor quality control, the first browsers to attempt support of CSS did a rather poor job of it.
The worst offenders are Microsoft Internet Explorer 3.x and Netscape Navigator 4.x. The first in their respective lines to attempt CSS support, these browsers have incomplete, bug-ridden, and quite often contradictory implementations of CSS1, never mind CSS2. These implementations are so bad that it is difficult to consider them CSS-supporting at all. Some of their flaws are bad enough to cause the browser to crash, or even lock up an entire system, when trying to handle some styles.
With Internet Explorer 4.x and 5.x, things did improve. Although not perfect by any means, these browser versions did at least stomp out many of the bugs that plagued IE3, and also added some support for previously unrecognized CSS properties in both CSS1 and CSS2.
Opera 3.5, on the other hand, came out of the gate with impressive CSS support. Confining itself to CSS1, this browser did quite well with the properties that it supported, suffering only a few minor bugs. When 3.6 was released, almost all of these bugs were eliminated, although support did not move past CSS1. Before version 3.5, Opera did not support CSS at all.
As for Netscape's products, the Navigator 4.7 is not significantly better at CSS support than was version 4.0, although it's at least less crash-prone. The only real hope for good CSS support out of Netscape is their Gecko rendering engine. As this was being written, the latest builds of Gecko were quite excellent, and were in fact used (along with Internet Explorer 4.5 and 5.0 for Macintosh) to create many of the figures in this book.
Since CSS is not intended to provide total control over document display, and should allow the page's content to come through no matter what browser is being used, this general state of affairs should not be considered a barrier to the use of CSS. You may wish, however, to warn your users that if they are using browsers of a certain vintage (Explorer 3.x, and perhaps Navigator 4.x) that they go into their preferences and disable style sheets. That way, they'll at least be able to read the content of your pages, even if it isn't styled the way you might have hoped.
Copyright © 2002 O'Reilly & Associates. All rights reserved.produce such color values, or for those who are familiar enough with the technical details of color generation to already think in terms of 0-255 values.
Then again, such people are probably more familiar with thinking in hexadecimal notation, which is what we turn to next.
188.8.131.52. Hexadecimal colors