I. Introduction
It may come as a surprise to some that, in early 2001, there is still a considerable number of people using Netscape 3.x as their preferred browser.  This can be interpreted in many ways: perhaps as a tribute to the robustness of that browser; perhaps as an indication of the size of the "late majority" (Geoffrey Moore, Crossing the Chasm) that resists change.

In any case, the web-site designer must be aware of this fact and plan accordingly.  In practice, this means either

1. requiring (and possibly enforcing) so-called "gen4" browsers (Netscape 4 or IE 4.01 or higher),
2. only using features supported in Netscape 3, or
3. write javascript code that detects the difference and takes appropriate action.

The rest of this document attempts to summarize the key differences between Netscape 3 and 4, and what (if anything) the site designer can do about it.  The document is divided up into general functional areas; pointers and links to detailed information are provided as appropriate.

This is very much a "work in progress" that reflects my experience with designing web-based tools from Netscape 1.0 on, plus additional input from other IBS staff.  Any and all feedback or information is welcome.  Please send it to roth@thedance.net.

 

II. Style Sheets
Style sheets (sometimes known as cascading style sheets, or CSS) are new in Netscape 4.  While style sheets are very useful as a way to provide consistent text formatting (with less work), one of the main uses of the CSS capability is to provide margin control of pages and images, and absolute positioning of text and graphic elements within a page.

All of this is non-existent in Netscape 3.  There is a slight amount of page margin control available to the Netscape 3 site designer via a kludge: putting a page inside a one-frame frameset.  But otherwise, we're stuck. (As an aside, note that there are many flaws in the implementation of style sheets in all of the gen4 browsers -- so CSS in gen4 isn't all roses, either.  For details, see www.oreilly.com/catalog/css/.)

 

III. Frames
Frames were first introduced in Netscape 3.  They work quite well, although the implementation is somewhat clunkier than the gen4 browser frame support.  The most important limitation: frame borders have a fixed size; they can not be made "invisible", or given different sizes or colors.  The result (of framesets viewed in Netscape 3) may appear ugly to many eyes, but at least it works.

 

IV. DHTML
DHTML, or "Dynamic HTML", is something of a misnomer.  What is commonly referred to as DHTML is a mixed bag of tricks involving absolute positioning, CSS, LAYERs, Javascript, and the IE DOM (document object model).  Neither Netscape 3 nor Netscape 4 implement true dynamic HTML, where the page can actually rewrite it's own content.

Nonetheless, the relevant limitation here for Netscape 3 is the lack of <LAYER> support.  LAYERs are what Netscape 4 uses to implement the seemingly-dynamic action of many "DHTML" features, such as the cascading hierarchical menus at www.webreference.com/dhtml/hiermenus/.

 

V. Tables
Issues about table tag support. Background images/colors?

 

VI. Javascript
Proper "defensive coding" technique for Javascript suggests that designers use constructs like:

   <SCRIPT LANGUAGE="JavaScript1.1">
   ...
   </SCRIPT>

so that browsers that do not support a particular version of Javascript will skip the relevant <SCRIPT> blocks. The mapping of Javascript version numbers to Netscape version numbers is straightforward:

• Javascript 1.0 is Netscape 2.0
• Javascript 1.1 is Netscape 3.0
• Javascript 1.2 is Netscape 4.0
  (Anyone know what Netscape 6 thinks?)

Most "core" Javascript features are available in Netscape 3, although there are many enhancements in Netscape 4.  A detailed comparison is available at developer.netscape.com/docs/manuals/communicator/jsguide/js1_2.htm.

I have a handfull of Javascript features that I really miss in Netscape 3; they include:

String.substr()	Extract a substring, easier than String.substring()
Screen	Info about the actual screen display
Window.resizeBy()	resizing an existing window

 

VII. Specific HTML tags
???

 

VIII. Plug-in issues
???

 

Appendix A: Links and References

1. Webmonkey has a very simple browser comparision chart that covers all browsers, at: hotwired.lycos.com/webmonkey/reference/browser_chart/.