Extensions: Love Em, Hate Em

Extensions: Love 'Em!, Hate 'Em!

HTML is standardized so that any Web browser can read any Web documents ” sort of.

Here's the deal: All modern browsers support all of HTML 4, a well-established set of tags set by the committees that oversee Internet standards. Standardization is good because it provides Web authors with a way to ensure that most browsers can read what they publish. Because any browser can understand and interpret all the HTML 4 tags, authors need only stick within the confines of those tags to ensure that their pages are accessible to the biggest possible online audience.

HTML 5 won't be created. Instead, the next major change in Web page standards is named XHTML. Similar to HTML in many respects, XHTML will give Web authors the level of control over page formatting that one sees in word processing and desktop publishing. XHTML is also being developed to accommodate the growing range of noncomputer devices that will be using the Web: portable phones and automobile Internet devices, for example.

The problem with standards, though, is that they evolve slowly. On the Web, only downloads are permitted to be slow; evolution is required to be fast. Think about it: The first graphical browser emerged seven years ago, and now we're talking real-time video. The entire birth and maturation of the Web as a graphical, interactive environment took place within the equivalent of a single Presidential administration. Yikes!

When creating pages for a company intranet, where all users may have the same browser, you may not need to consider the extensions issue ”you can apply all tags supported by the browser.

Leading browsers, including both Netscape and Internet Explorer, support all of HTML 4, the current standard. Still, the pace of Web page enhancement is so great that both Netscape and Microsoft continue to incorporate in their browsers extra tags and other capabilities that are not part of any approved HTML standard. These additional tags are extensions.

An extension is an HTML tag that makes possible some new capability in a Web page but is not yet part of the formal HTML standard.

The effects of these extensions, when used in a Web document, can usually be seen only through a browser that specifically supports them. Of course, Navigator supports many Netscape extensions, and Internet Explorer supports many Microsoft extensions. But subtle differences exist. For example, scrolling text banners that can appear in a box in the page layout in Internet Explorer appear instead in the status bar in some versions of Netscape. However, not all browsers support all extensions. That's why you need to be careful with 'em.

In general, whenever an incompatible browser accesses a page that uses these tags, nothing dire happens. The fancy extension-based formatting doesn't show up, but the meat of the page ”its text and graphics ” remain readable.

Authors who want to take advantage of extensions are concerned that some visitors are not seeing the page in its full glory . That's why, more and more, you see messages like "Best when viewed through Netscape Navigator" or "Enhanced for Internet Explorer" on Web pages. That's the author's way of telling you that he or she has used extensions ”and if you want to enjoy all the features of the page, you had better pick up a compatible browser.