DHTML: Visual QuickStart Guideby Jason Cranford Teague, Simon Hayes (Editor)
Easy to use and also comprehensive. The DHTML Visual QuickStart Guide documents every aspect of this complex technology, and provides extensive appendices that make finding the exact code word you need a snap.
Read an Excerpt
Who is this book for? If the title of this book caught your eye, you're probably already well acquainted with the ins and outs of the Internet's most popular off shoot, the World Wide Web-or perhaps just a severely confused arachnophile. In order to understand this book, you will need to be familiar with the HyperText Mark-up Language. You don't have to be an expert, but you should at least know the difference between a
tag and a
What is Dynamic HTML?
So the real question is, what makes a Web page dynamic? There is, of course, substantial debate on this topic, but we can agree on a few things.
- Dynamic documents allow the designer to control how the HTML displays the Web pages' content.
- Dynamic documents react and change with the actions of the visitor (the person using the Web site).
- Dynamic documents can exactly position any element in the window, and change that position after the document has loaded.
- Dynamic documents can hide and show content as needed.
The flavors of DHTML
Unfortunately, Netscape and Microsoft have differing ideas about exactly what technologies should be used to make HTML more dynamic. Fortunately for us, the specifications of these two companies do overlap, as shown in Figure I.1. And this area of overlap is what this book is primarily about. Why? Because the World Wide Web was founded on a very simple premise: the display of Web documents should be indifferent to the software being used.
Evolution and progress mean newer browsers have had to add technologies not supported by legacy (older) browsers. Still, there is an important tenet supporting the idea of being able to use the Web regardless of whose binary code you happen to be running. Cross-browser capability is what the Web is all about, and for good reason.
The following technologies will run pretty much identically, regardless of the DHTML browser being used. (Exceptions are noted throughout this book.)
- Cascading Style Sheets (CSS), Level 1 CSS allows you to define how HTML tags should display their content.
- Cascading Style Sheets-Positioning (CSS-P) With CSS-P you can exactly position HTML elements anywhere in the window, as well as control the visibility of those elements.
- Layers: Like CSS-P, layers allow you to control the position of elements on the screen and their visibility. Microsoft-Specific DHTML Much of the Microsoft-specific DHTML is based on proprietary Microsoft software, such as ActiveX technology. Since ActiveX is owned by Microsoft, it is unlikely that it will ever be a cross-browser technology.
- Visual Filters: Visual filters let you perform visual effects on graphics and text in your document. If you have ever worked with Photoshop filters, you'll understand the similar ways of visual filters.
- Dynamic CSS: With Internet Explorer you can not only change the positions of elements on the screen, you can change their visual appearance as well.
- CSS and DHTML: By the beginning of the next millennium, a scant two years away, the Web will probably bear no more resemblance to its current incarnation than a telephone does to an aldus lamp. The technologies used to create Web pages will continue to evolve, especially in the visual range. One thing Web design has always lacked however, especially for anyone used to the controls available in desktop layout programs such as PageMaker and Quark, is exact control over the position and appearance of the HTML elements on the screen. Cascading Style Sheets,-the key component of cross-browser DHTML technology and a central topic of this book-allow for just such control over our Web pages. Although the concept of control may not seem as jazzy and dynamic as the ability to make graphics move around on the page, CSS has the potential to do for Web layout what word processors did for print publication. In addition, the dynamic capabilities of cross browser DHTML are all predicated on the use of Cascading Style Sheet-Positioning.
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