HTML The Definitive Guide (59 page)
Read HTML The Definitive Guide Online
Authors: Chuck Musciano Bill Kennedy
5.5.1.1 The align attribute
Internet Explorer places
The align attribute accepts a value of top, middle, or bottom, meaning that the specified point of the marquee will be aligned with the corresponding point in the surrounding text. Thus:
aligns the top of the marquee area with the top of the surrounding text. Also see the height and width, hspace, and vspace attributes (later in this chapter), which control the dimensions of the marquee.
5.5.1.2 The behavior, direction, and loop attributes
Together, these three attributes control the style, direction, and duration of the scrolling in your marquee.
The behavior attribute accepts three values: scroll (default)
The value of scroll causes the marquee to act like the grand marquee in Times Square: the marquee area is empty initially; the text then scrolls in from one side (controlled by the direction attribute), continues across until it reaches the other side of the marquee, and then scrolls off until the marquee is once again empty.
slide
This value causes the marquee to start empty. Text then scrolls in from one side (controlled by the direction attribute), stops when it reaches the other side, and remains onscreen.
alternate
Specifying alternate as the value for the behavior attribute causes the marquee to start with the text fully visible at one end of the marquee area. The text then scrolls until it reaches the other end, whereupon it reverses direction and scrolls back to its starting point.
If you do not specify a marquee behavior, the default behavior is scroll.
The direction attribute sets the direction for marquee text scrolling. Acceptable values are either left (the default) or right. Note that the starting end for the scrolling is opposite to the direction: left means that the text starts at the right of the marquee and scrolls to the left. Remember also that rightward-scrolling text is counterintuitive to anyone who reads left to right.
The loop attribute determines how many times the marquee text scrolls. If an integer value is provided, the scrolling action is repeated that many times. If the value is infinite, the scrolling repeats until the user moves on to another document within the browser.
Putting some of these attributes together:
.......... Taste great, too!
The example message starts at the right side of the display window (default), scrolls leftward all the way across and off the Internet Explorer display, and then starts over again until the user moves on to another page. Notice the intervening periods and spaces for the "trailer"; you can't append one marquee to another.
Also, the slide-style of scrolling looks jerky when repeated and should only be scrolled once. Other scrolling behaviors work well with repeated scrolling.
5.5.1.3 The bgcolor attribute
The bgcolor attribute lets you change the background color of the marquee area. It accepts either an
RGB color value or one of the standard color names. See Appendix F for a full discussion of both
color-specification methods.
To create a marquee area whose color is yellow, you would write:
5.5.1.4 The height and width attributes
The height and width attributes determine the size of the marquee area. If not specified, the marquee area extends all the way across the Internet Explorer display and will be just high enough to enclose the marquee text.
Both attributes accept either a numeric value, indicating an absolute size in pixels, or a percentage, indicating the size as a percentage of the browser window height and width.
For example, to create a marquee that is 50 pixels tall and occupies one-third of the display window width, use:
5.5.1.5 The hspace and vspace attributes
The hspace and vspace attributes let you create some space between the marquee and the surrounding text. This usually makes the marquee stand out from the text around it.
Both attributes require an integer value specifying the space needed in pixels. The hspace attribute creates space to the left and right of the marquee; the vspace attribute creates space above and below the marquee. To create 10 pixels of space all the way around your marquee, for example, use:
5.5.1.6 The scrollamount and scrolldelay attributes
These attributes control the speed and smoothness of the scrolling marquee.
The scrollamount attribute value is the number of pixels needed to move text each successive movement during the scrolling process. Lower values mean smoother, but slower scrolling; higher numbers create faster, but jerkier text motion.
The scrolldelay attribute lets you set the number of milliseconds to wait between successive movements during the scrolling process. The smaller this value, the faster the scrolling.
You can use a low scrolldelay to mitigate the slowness of a small, smooth scrollamount.
For example:
5.4 Background Audio
5.6 Other Multimedia Content
5.6 Other Multimedia Content
The Web is completely open-minded about the types of content that can be exchanged by servers and browsers. In this section, we look at a different way to reference images, along with audio, video, and other document formats.
5.6.1 Embedded Versus Referenced Content
Images currently enjoy a special status among the various media that can be included within an HTML document and displayed inline with other content by all but a few browsers. Sometimes, however, as we discussed earlier in this chapter, you may also reference images externally, particularly large ones in which details are important, but not immediately necessary to the document content. Other multimedia elements, including digital audio and video, can be referenced as separate documents external to the current one.
You normally use the anchor tag () to link external multimedia elements to the current document. Just like other link elements selected by the user, the browser downloads the multimedia object and presents it to the user, possibly with the assistance of an external application or plug-in. Referenced content is always a two-step process: present the document
that links to the desired multimedia object, then present the object if the user selects the link. [, 7.3]
In the case of images, you can choose how to present images to the user: inline and immediately available via the tag, or referenced and subsequently available via the tag. If your images are small and critical to the current document, you should provide them inline. If they are large or are only a secondary element of the current document, make them available as referenced content via the tag.