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Get Ready for Dynamic HTML

-- by Warren Ernst

The blinking text that's been lighting up your browser screen for the past year is already passe. It'll be even more so with the release of version 4.0 browsers from Netscape and Microsoft, which will be capable of reading scripted HTML code dubbed "Dynamic HTML."

Still under discussion at the World Wide Web Consortium (W3C), the Dynamic HTML standard describes a way to divide portions of a Web page into different elements or objects. Designers can independently position these elements in sequence within a browser window, creating effects such as a headline that flies letter by letter from the left edge of the browser window into the center of the screen. Other effects include layering, where one element sits under or above another, making transparent effects possible; absolute positioning, where an element has specific x and y coordinates that fix it at a particular place on the screen; data manipulation, which allows a developer to program ways for the browser to display subsets of a database query without requiring another server request; and simple GIF animations, like rotation.

Specification wars

With the specification still up in the air, Netscape and Microsoft are continuing to fight about the details of Dynamic HTML, and have built their 4.0 browsers to take advantage of the implementations they prefer. Both companies, however, have stated that they would fully support the official specification.

Netscape's initial implementation of Dynamic HTML involves a Netscape-specific Layer tag, combined with JavaScript Accessible Style Sheets (JASS). The tag allows positioning and overlapping of segments of an HTML file, and JASS modifies those segments on the fly when the page loads and in response to user interaction.

Microsoft proposes extending Cascading Style Sheets (CSS), which already exist as an HTML standard. With CSS, a Web page designer can redefine HTML tags using either a linked external CSS file (which, like HTML, is a plain-text file), or employing the new Style tag embedded within the HTML file's Header section. For example, TechWeb, CMP Media's technology supersite, can decide to make everything with an H1 headline tag appear with a yellow background, as if marked with a fluorescent highlighter. This change would affect every bit of text tagged "H1," and it could affect every Web page on a site, making consistency and site management much easier.

Extending CSS to objects

Under Microsoft's scheme, CSS is extended to allow for exact positioning of elements, and the Web page itself is broken down into well-defined objects (think object-oriented programming) whose properties can be manipulated at any time by any scripting language, such as JavaScript or VBScript. Microsoft also includes a series of scriptable ActiveX controls (think platform-specific Java applets) with IE 4.0; these controls produce multimedia effects that Dynamic HTML can alter.

What does all this mean to Web page developers? Since both Netscape and Microsoft will adhere to the guidelines set forth by the W3C, developers should do what they've always done-create pages that work with either browser. Netscape says it will still support its proprietary Layer tags, but since pages using this tag won't look right under IE, designers risk alienating their audience if they use it. Most likely, Layer will become the dinosaur that Microsoft's Marquee tag is.

As a Web surfer, you can look forward to a new level of-well, dynamic Web pages. Your browsing might even become faster, because most of the processing will be done on your computer-you won't have to wait for the long trip back to the server to get the next frame in a dynamic sequence. Of course, you won't see many such dynamic pages at this moment: The technology is still too new to have spread far. But you probably won't have to wait long; remember how quickly leading-edge Web sites outgrew the Blink tag.

Windows Magazine, June 1997, page 136.

[ Go to June 1997 Table of Contents ]