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10.4. Generated Content

Generated content is a new way of adding things to existing content without having to alter the content itself. It's done by using the pseudo-elements :before and :after and the property content. Here's a basic example of how it works:

P:before, P:after {content: "\""; color: gray;}
<P>This is a quote.</P>

The browser will display what's shown in Figure 10-15.

Figure 10-15

Figure 10-15. Adding generated content

Note that the double-quote mark was escaped out -- that is, preceded by a backslash. This is necessary, since text values for content must be enclosed in double quotes. You could also place images before (or after) content, using something like P:before {content: url(para.gif);} to put a paragraph symbol at the beginning of each paragraph. You can even string multiple values together like this (shown in Figure 10-16):

P:before {content: url(para.gif) " -- ";}
Figure 10-16

Figure 10-16. Adding an image and text before a paragraph

This would cause each paragraph to be started with a paragraph symbol, a blank space, two dashes, and then another blank space. Note that all of this is considered part of the paragraph and is inlined within it. The spaces appear before and after the double dash because they're included in the string value. If these spaces were omitted, then space would not appear to either side of the dashes.

Let's say, though, that you want to do some real quoting, using real quotation marks -- you know, the curly double quotes that are so hard to specify in HTML and which often don't show up even if you do try to specify them. CSS2 has ways to handle this.

content has some other values you can use:

So if you wanted your quotations to begin and end with quotation marks, instead of typing in a literal quotation mark, you could let the browser insert "smart quotes" for you.

BLOCKQUOTE:before {content: open-quote;}
BLOCKQUOTE:after {content: close-quote;}

10.4.1. Automatic Numbering

In the same vein, CSS2 also includes properties for automatic numbering. First, you can specify a counter as a value of content. This can be a bit tricky, and it would take too long to run through all the possibilities, but here's an example. Say you wanted the chapters and sections of a document numbered 1, 1.1, 1.2, 1.3, and so on. In addition, you're using H1 for your chapters and H2 for your sections. Here are the declarations you would use:

H1:before {
content: "Chapter " counter(chapter) ". ";
counter-increment: chapter;   /* Add 1 to chapter */
counter-reset: section;       /* Set section to 0 */
}
H2:before {
content: counter(chapter) "." counter(section) " ";
counter-increment: section;
}

As we can see from Figure 10-17, the user agent will add the word "Chapter" and a number at the beginning of H1 text. This number is automatically incremented with each H1, due to the declaration counter-increment: chapter;. It also sets the section counter back to zero through counter-reset: section;. Then, for each section heading (H2), the browser uses the chapter number, followed by a period (.) followed by the current section number, which is also automatically incremented.

Figure 10-17

Figure 10-17. Adding counters to elements

You don't have to increment by one every time, either. You can define any integer as the increment value, including zero and negative numbers. If you want each section to have an even number, as we see in Figure 10-18, then you can declare the following:

H2:before {
content: "Section " counter(section) ". ";
counter-increment: section 2; /* Add 2 to chapter */
cover all the bases in a compact manner, we declare:

H1, H2, H3, H4, H5, H6 {font-family: Verdana,sans-serif;}H1 {color: rgb(0%,40%,0%); border-bottom: thin solid; width: 100%;}

With the second declaration, not only do we use the standard color,but we enhance the idea of "underlining" by setting abottom border that will extend from the left edge of the text all theway out to the right edge of the browser window. This line will alsoinherit the green color of the text and so really punch up the factthat the title and navigation buttons are separate from the rest of }

Figure 10-18

Figure 10-18. Changing a counter's incremental value

You can also keep an element from incrementing a counter by setting its display to none. Of course, that will cause the element to disappear altogether.

10.4.2. Markers

You can do even more by using the value marker for the property display, which enables you to define your own marker styles for any element at all. You're already familiar with markers, as it happens -- the bullets and numbers at the beginning of list items are markers.

Let's say we want to recreate the way unordered lists behave. For the purposes of this example, we'll use the image disc.gif to stand in for the normal bullets. Using marker properties, we would declare:

LI:before {display: marker;
content: url(disc.gif);
marker-offset: 1em;
}

This will insert the disc image before each list item, and set it to be offset from the left edge of the LI content by 1em, as shown in Figure 10-19.

Figure 10-19

Figure 10-19. Styling list markers

Marker properties are not restricted to list items, however. Let's say that, throughout a document, there are a few paragraphs with a class of aside. We wish to call attention to these paragraphs by inserting a small note to the side of each one. Here's one way to do it:

BODY {counter-reset: aside-ctr;}
P {margin-left: 10em;}
P.aside:before {display: marker;
content: "Aside " counter(aside-ctr) " --";
counter-increment: aside-ctr;
text-align: right;
marker-offset: 1em;
width: 9.5em;
}

The effect will be something like that seen in Figure 10-20.

Figure 10-20

Figure 10-20. Automatically numbered asides

This is yet another aspect of CSS2 that, once it's been properly implemented, will allow authors to do quite a bit with their documents.



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floated element is wider than its parent. In that case, the floatedelement will simply overrun the right or left inneredge -- depending on which way the element is floated -- in itsbest attempt to display itself correctly. This will lead to a resultlikethatshown in Figure 8-44.

Figure 8-44

Figure 8-44. Floating an element that is wider than its parent

1.4.1.1. LINK attributes

For the rest of the LINKtag, the attributes and values are fairly straightforward.REL stands for "relation," and in thiscase, the relation is "stylesheet."TYPE is alwaysset to text/css. This value describesthe type of data that is to be loaded using the to stop there. For example:

P.starry{background-image: url(http://www.site.web/pix/stars.gif);color: white;}<P CLASS="starry">It's the end of autumn, which means the stars will bebrighter than  ever!  Join us...

As we can see in Figure 6-23, a background has beenapplied to a single paragraph and no other part of the document.

Figure 6-23

Figure 6-23. Applying a background image for a single element

simply set the BODY contents to be flowed into twocolumns. Unfortunately, CSS2 contains no provisions for
columns or column flow. There have beendiscussions in the CSS community about adding such behaviors to CSS,and perhaps they will be added in the future. For now, we'reforced to do things like add DIVs to representcolumns.

This assumes that you wish to create columns at all, of course. Wewent to a great deal of effort to get those columns, but was itas an image. UnderCSS2, it is possible to set up asituation where scrollbars would be applied to an element such as aparagraph.

It's also possible to set the top and bottom margins of ablock-level element to be auto. If either of theseproperties is set to auto, it is reset to0 (zero), effectively removing any top or bottom