Tự học HTML và CSS trong 1 giờ - part 17 docx

ptg You can nest character tags—for example, using both bold and italic for a set of charac- ters—as follows: <b><i>Text that is both bold and italic</i></b> However, the result on the screen is browser-dependent, like all HTML tags. You won’t necessarily end up with text that’s both bold and italic. You might end up with one style or the other: Input ▼ <p>In Dante’s <i>Inferno</i>, malaboge was the eighth circle of hell, and held the malicious and fraudulent.</p> <p>All entries must be received by <b>September 26, 1999</b>.</p> <p>Type <tt>lpr -Pbirch myfile.txt</tt> to print that file.</p> <p>Sign your name in the spot marked <u>Sign Here</u>:</p> <p>People who wear orange shirts and plaid pants <s>have no taste</s> are fashion-challenged.</p> <p>RCP floor mats give you <big>big</big> savings over the competition!</p> <p>Then, from the corner of the room, he heard a <small>tiny voice </small>.</p> <p>In heavy trading today. Consolidated Orange Trucking rose ¹/₄ points on volume of 1,457,900 shares.</p> Figure 7.2 shows some of the physical tags and how they appear. 136 LESSON 7: Formatting Text with HTML and CSS Output . FIGURE 7.2 Physical styles displayed in a browser. Download from www.wowebook.com ptg Character Formatting Using CSS You’ve already seen how styles can modify the appearance of various elements. Any of the effects associated with the tags introduced in this lesson can also be created using CSS. Before I go into these properties, however, I want to talk a bit about how to use them. As I’ve said before, the style attribute can be used with most tags. However, most tags somehow affect the appearance of the text that they enclose. There’s a tag that does- n’t have any inherent effect on the text that it’s wrapped around: the <span> tag. It exists solely to be associated with style sheets. It’s used exactly like any of the other tags you’ve seen in this lesson. Simply wrap it around some text, like this: <p>This is an example of the <span>usage of the span tag</span>.</p> Used by itself, the <span> tag has absolutely no effect. Paired with the style attribute, it can take the place of any of the tags you’ve seen in this lesson and can do a lot more than that, as well. The Text Decoration Property The text-decoration property is used to specify which, if any, decoration will be applied to the text within the affected tag. The valid values for this property are underline, overline, line-through, and blink. The application of each of them is self-explanatory. However, here’s an example that demonstrates how to use each of them: <p>Here is some <span style=’text-decoration: underline”>underlined text</span>.</p> <p>Here is some <span style=”text-decoration: overline”>overlined text</span>.</p> <p>Here is some <span style=”text-decoration: line-through”>line-through text</span>.</p> <p>Here is some <span style=”text-decoration: blink”>blinking text</span>.</p> The cool thing is that you can use this, and all the properties you’ll see in this lesson, with any tag that contains text. Take a look at this example: <h1 style=”text-decoration: underline”>An Underlined Heading</h1> Using the style attribute, you can specify how the text of the heading appears. Choosing between this approach and the <u> tag is a wash—if you want to remove the underlining from the heading, you have to come back and edit the tag itself, regardless of whether you used the <u> tag or style attribute. Later, you’ll see how to use style sheets to control the appearance of many elements simultaneously. Character Formatting Using CSS 137 7 Download from www.wowebook.com ptg Font Properties When you want to modify the appearance of text, the other major family of properties you can use is font properties. You can use font properties to modify pretty much any aspect of the type used to render text in a browser. One of the particularly nice things about font properties is that they’re much more specific than the tags that you’ve seen so far. First, let’s look at some of the direct replacements for tags you’ve already seen. The font-style property can be used to italicize text. It has three possible values: normal, which is the default; italic, which renders the text in the same way as the <i> tag; and oblique, which in theory is somewhere between italic and normal, and is rendered by nearly all browsers as regular italics. Here are some examples: <p>Here’s some <span style=”font-style: italic”>italicized text</span>.</p> <p>Here’s some <span style=”font-style: oblique”>oblique text</span> (which may look like regular italics in your browser).</p> Now let’s look at how you use CSS to create boldfaced text. In the world of HTML, you have two options: bold and not bold. With CSS, you have (theoretically) many more options. The reason I say theoretically is that browser support for the wide breadth of font weights available using CSS can be spotty. To specify that text should be boldface, the font-weight property is used. Valid values are normal (the default), bold, bolder, lighter, and 100 through 900, in units of 100. Here are some examples: <p>Here’s some <span style=”font-weight: bold”>bold text</span>.</p> <p>Here’s some <span style=”font-weight: bolder”>bolder text</span>.</p> <p>Here’s some <span style=”font-weight: lighter”>lighter text</span>.</p> <p>Here’s some <span style=”font-weight: 700”>bolder text</span>.</p> You can also set the typeface for text using the font-family property. In addition, you can set the specific font for text, but I’m not going to discuss that until later in the lesson. In the meantime, let’s look at how you can set the font to a member of a particular font family. The specific font will be taken from the user’s preferences. The property to mod- ify is font-family. The possible values are serif, sans-serif, cursive, fantasy, and monospace. So, if you want to specify that a monospace font should be used with CSS rather than the <tt> tag, you use the following code: <p><span style=”font-family: monospace”>This is monospaced text.</span></p> Now let’s look at one capability not available using regular HTML tags. Using the font- variant property, you can have your text rendered so that lowercase letters are replaced with larger capital letters. The two values available are normal and small-caps. Here’s an example: <p><span style=’font-variant: small-caps’>This Text Uses Small Caps.</span></p> 138 LESSON 7: Formatting Text with HTML and CSS Download from www.wowebook.com ptg The web page in Figure 7.3 contains some text that uses the font-variant property as well as all the other properties described in this section. Preformatted Text 139 7 Output . FIGURE 7.3 Text styled using CSS. Preformatted Text Most of the time, text in an HTML file is formatted based on the HTML tags used to mark up that text. In Lesson 3, “Introducing HTML and XHTML,” I mentioned that any extra whitespace (spaces, tabs, returns) that you include in your HTML source is stripped out by the browser. The one exception to this rule is the preformatted text tag <pre>. Any whitespace that you put into text surrounded by the <pre> and </pre> tags is retained in the final output. With these tags, the spacing in the text in the HTML source is preserved when it’s dis- played on the page. The catch is that preformatted text usually is displayed (in graphical displays, at least) in a monospaced font such as Courier. Preformatted text is excellent for displaying code examples in which you want the text formatted with exactly the indentation the author used. Because you can use the <pre> tag to align text by padding it with spaces, you can use it for simple tables. However, the fact that the tables are presented in a monospaced font might make them less than ideal. (You’ll learn how to create real tables in Lesson 10, “Building Tables.”) The following is an example of a table created with <pre>: Download from www.wowebook.com ptg Input ▼ <pre> Diameter Distance Time to Time to (miles) from Sun Orbit Rotate (millions of miles) ———————————————————————————————————— Mercury 3100 36 88 days 59 days Venus 7700 67 225 days 244 days Earth 7920 93 365 days 24 hrs Mars 4200 141 687 days 24 hrs 24 mins Jupiter 88640 483 11.9 years 9 hrs 50 mins Saturn 74500 886 29.5 years 10 hrs 39 mins Uranus 32000 1782 84 years 23 hrs Neptune 31000 2793 165 days 15 hrs 48 mins Pluto 1500 3670 248 years 6 days 7 hrs </pre> Figure 7.4 shows how it looks in a browser. 140 LESSON 7: Formatting Text with HTML and CSS Output . FIGURE 7.4 A table created using <pre>, shown in a browser. When you’re creating text for the <pre> tag, you can use link tags and character styles but not element tags such as headings or paragraphs. You should break your lines with hard returns and try to keep your lines to 60 characters or fewer. Some browsers might have limited horizontal space in which to display text. Because browsers usually won’t reformat preformatted text to fit that space, you should make sure that you keep your text within the boundaries to prevent your readers from having to scroll from side to side. Be careful with tabs in preformatted text. The actual number of characters for each tab stop varies from browser to browser. One browser might have tab stops at every fourth character, whereas another may have them at every eighth character. You should convert any tabs in your preformatted text to spaces so that your formatting isn’t messed up if it’s viewed with different tab settings than in the program you used to enter the text. Download from www.wowebook.com ptg The <pre> tag is also excellent for converting files that were originally in some sort of text-only form, such as mail messages or Usenet news postings, into HTML quickly and easily. Just surround the entire content of the article within <pre> tags and you have instant HTML, as in the following example: <pre> To: lemay@lne.com From: jokes@lne.com Subject: Tales of the Move From Hell, pt. 1 I spent the day on the phone today with the entire household services division of northern California, turning off services, turning on services, transferring services and other such fun things you have to do when you move. It used to be you just called these people and got put on hold for and interminable amount of time, maybe with some nice music, and then you got a customer representative who was surly and hard of hearing, but with some work you could actually get your phone turned off. </pre> One creative use of the <pre> tag is to create ASCII art for your web pages. The follow- ing HTML input and output example shows a simple ASCII-art cow: Input ▼ <pre> ( ) Moo (oo) \/———\ || | \ ||—-W|| * || || </pre> Figure 7.5 displays the result. Preformatted Text 141 7 Download from www.wowebook.com ptg Output . FIGURE 7.5 A bit of ASCII art that illustrates how preformatted text works. 142 LESSON 7: Formatting Text with HTML and CSS Horizontal Rules The <hr> tag, which has no closing tag in HTML and no text associated with it, creates a horizontal line on the page. Rule lines are used to visually separate sections of a web page—just before headings, for example, or to separate body text from a list of items. Closing Empty Elements The <hr> tag has no closing tag in HTML. To convert this tag to XHTML and to ensure compatibility with HTML browsers, add a space and a forward slash to the end of the tag: <hr /> If the horizontal line has attributes associated with it, the forward slash still appears at the end of the tag, as shown in the following examples: <hr size=”2” /> <hr width=”75%” /> <hr align=”center” size=”4” width=”200” /> The following input shows a rule line and a list as you would write it in XHTML 1.0: Input ▼ <hr /> <h2>To Do on Friday</h2> <ul> <li>Do laundry</li> <li>Send FedEx with pictures</li> <li>Have lunch with Mollie</li> <li>Read Email</li> <li>Set up Ethernet</li> </ul> <hr /> Download from www.wowebook.com ptg Figure 7.6 shows how they appear in a browser. Horizontal Rules 143 7 Output . FIGURE 7.6 An example of how horizontal rules are used around a list. Attributes of the <hr> Tag There are a number of attributes that can be used to modify the appearance of a horizon- tal rule. Although they work in current browsers, they have been removed from HTML5, and you should use CSS instead. The size attribute indicates the thickness, in pixels, of the rule line. The default is 2, and this also is the smallest that you can make the rule line. Figure 7.7 shows the sample rule line thicknesses created with the following code: Input ▼ <h2>2 Pixels</h2> <hr size=”2” /> <h2>4 Pixels</h2> <hr size=”4” /> <h2>8 Pixels</h2> <hr size=”8” /> <h2>16 Pixels</h2> <hr size=”16” /> Output . FIGURE 7.7 Examples of rule line thicknesses. Download from www.wowebook.com ptg To change the thickness of an <hr> with CSS, use the height attribute, which I’ll discuss in Lesson 8, “Using CSS to Style a Site.” The width attribute specifies the horizontal width of the rule line. You can specify the exact width of the rule in pixels. You can also specify the value as a percentage of the browser width (for example, 30% or 50%). If you set the width of a horizontal rule to a percentage, the width of the rule will change to conform to the window size if the user resizes the browser window. Alternatively, you can use the width CSS property instead. I’ll also talk about width in the following lesson. Figure 7.8 shows the result of the fol- lowing code, which displays some sample rule line widths: Input ▼ <h2>100%</h2> <hr /> <h2>75%</h2> <hr width=”75%” /> <h2>50%</h2> <hr width=”50%” /> <h2>25%</h2> <hr width=”25%” /> <h2>10%</h2> <hr width=”10%” /> 144 LESSON 7: Formatting Text with HTML and CSS Output . FIGURE 7.8 Examples of rule line widths. If you specify a width smaller than the actual width of the browser window, you can also specify the alignment of that rule with the align attribute, making it flush left (align=”left”), flush right (align=”right”), or centered (align=”center”). By default, rule lines are centered. The align attribute has been removed from HTML5 for all ele- ments that once supported it. Aligntment will be covered in the following lesson. Download from www.wowebook.com ptg Finally, in most current browsers, the noshade attribute shown in the following example causes the browser to draw the rule line as a plain line without the three-dimensional shading, as shown in Figure 7.9. Line Break 145 7 Handling Attributes Without Values In HTML 4.01 and, more recently, HTML5, a value isn’t required by the noshade attribute. The method you use to apply this attribute appears as follows: <hr align=”center” size=”4” width=”200” noshade> To comply with XHTML 1.0, however, all attributes require a value. The HTML 4.01 specification requires that Boolean attributes (such as noshade) have only the name of the attribute itself as the value. The following example demonstrates how to apply the noshade attribute to the <hr> tag in compliance with the XHTML 1.0 specifica- tion. To comply with HTML5, you would drop all of the attributes and use CSS instead. (The noshade attribute can be duplicated by changing the borders and back- ground of the horizontal rule.) <hr align=”center” size=”4” width=”200” noshade=”noshade” /> <hr align=”center” size=”4” width=”300” noshade=”noshade” /> <hr align=”center” size=”4” width=”400” noshade=”noshade” /> <h1 align=”center”>NorthWestern Video</h1> <hr align=”center” size=”4” width=”400” noshade=”noshade” /> <hr align=”center” size=”4” width=”300” noshade=”noshade” /> <hr align=”center” size=”4” width=”200” noshade=”noshade” /> <h2 align=”center”>Presents</h2> Output . FIGURE 7.9 Rule lines without shading. Line Break The <br> tag breaks a line of text at the point where it appears. When a web browser encounters a <br> tag, it restarts the text after the tag at the left margin (whatever the current left margin happens to be for the current element). You can use <br> within other elements, such as paragraphs or list items; <br> won’t add extra space above or below the new line or change the font or style of the current entity. All it does is restart the text at the next line. Download from www.wowebook.com . years 10 hrs 39 mins Uranus 32000 17 82 84 years 23 hrs Neptune 310 00 2793 16 5 days 15 hrs 48 mins Pluto 15 00 3670 248 years 6 days 7 hrs </pre> Figure 7.4 shows how it looks in a browser. 14 0 LESSON. with the XHTML 1. 0 specifica- tion. To comply with HTML5 , you would drop all of the attributes and use CSS instead. (The noshade attribute can be duplicated by changing the borders and back- ground. example: <p><span style=’font-variant: small-caps’>This Text Uses Small Caps.</span></p> 13 8 LESSON 7: Formatting Text with HTML and CSS Download from www.wowebook.com ptg The