How to Design for Different Browsers | 2 | WebReference

How to Design for Different Browsers | 2

How to Design for Different Browsers

Rendering Engines

A rendering engine, also known as a layout engine, is the code that tells the browser how to display web content and available style information in the browser window. The rendering engine is responsible for the size of an unstyled h1 heading or how a horizontal rule looks on the page. It's also the key to the correct implementation of CSS and other web standards.

The first separate and reusable rendering engine was Gecko , released by the Mozilla developers in 1998. It was notable for its small size and excellent support for standards. Now web developers pay attention to underlying rendering engines as a key to understanding a browser's performance.

The Wikipedia, an online collaborative encyclopedia, has a detailed comparison of rendering engines, where they are used, and what they support at

Browser Roll-Call

It is critical that professional web developers be familiar with the most popular browsers in current use and not just the ones on their own desktops. This section provides basic information about the browsers that web developers care about most, whether because of total share of web usage (Internet Explorer 6 for Windows) or because its technology and standards support is important to the development community (Opera). The browsers listed here make up more than 99% of total usage as of this writing.


There are scores of less common browsers, some with loyal followings, as well as older browser versions that are still in use. Unfortunately, it is not possible to list them all in this chapter., a site for the web development community, keeps a complete archive of browsers old and new at

Table 2-1 lists the browsers and their release dates, platforms, rendering engines, and level of standards support, while the following sections describe each browser in more detail.

Table 2-1. Various web browsers


Release date


Rendering engine

Standards support

Microsoft Internet Explorer 6


Windows, Linux, Unix

Trident IV

CSS 1, some CSS 2, some CSS 3, ECMAScript, DOM (with proprietary implementations and quirks)

Microsoft Internet Explorer 5 and 5.5 (Windows)

1999 (5), 2001 (5.5)

Windows, Linux, Unix

Trident II (5) and III (5.5)

Most CSS 1, some CSS 2 (with bugs), partial support of ECMAScript/DOM

Microsoft Internet Explorer 5 (Macintosh)




CSS 1, some CSS 2, some CSS 3, ECMAScript, DOM (buggy and not complete)

Netscape Navigator 7


Windows, Macintosh, Linux, Unix



CSS 1, most CSS 2, ECMAScript, DOM

Netscape Navigator 4


Windows, Linux, Macintosh, Unix


Some basic CSS 1, JavaScript, no DOM because it was written after NN4's release

Firefox 1.0

2005 (pre 1.0 release versions available in 2004)

Windows, Linux, Macintosh, Unix


CSS 1, most CSS 2, some CSS 3, ECMAScript, DOM

Opera 8.5


Windows, Linux, Macintosh, Unix


CSS 1, most CSS 2, ECMAScript, DOM (Opera 7 was the first version with DOM support)



Macintosh OS X


most CSS 1, some CSS 2, some CSS 3, ECMAScript, DOM (with bugs)

America Online


Windows (there is a Mac version, but it isn't as well supported)


CSS 1, some CSS 2, ECMAScript, DOM (same as Internet Explorer, but expect additional buggy behavior)



Unix, Windows, Macintosh



Internet Explorer 6 is the browser that comes with Windows XP, although it is also available for older Windows versions. As this book goes to press, Version 6 alone currently accounts for more than half of all web usage. Unfortunately, it is also notorious for inconsistent standards support. Microsoft has plans to release IE 7, which promises better security (the Achilles' heel of previous versions) and better standards support, with special attention to Cascading Style Sheets Level 2.1.

For information on designing for Internet Explorer, visit Microsoft's Internet Explorer Developer Center (part of its MSDN online developer's network) at Additional information is available on the Microsoft product pages at

Released in early 1999, IE 5 was the first major browser with XML support. Because it is tied to several older Windows versions, it still accounts for 5 to 10% of browser usage as of this writing.

Internet Explorer 5 for the Macintosh was released in 2000 and offered never before seen high levels of standards compliance and features that even IE 6 for Windows has yet to match. Microsoft stopped development with Version 5.2.3 but still offers free downloads of the latest versions of IE 5/Mac for OS X (5.2.3) and OS 9 (5.1.7).

This latest version of Navigator was released in 2002, with additional 7.x releases in 2003 and 2004. It is essentially the Mozilla browser wrapped in the Netscape brand. It accounts for a startlingly small share of web traffic (less than 1%). Netscape's previous meaningful release was Version 6, which was years in the making, had numerous problems with standards and failed to gain back the market share gobbled up by Internet Explorer during its overlong development. A beta of Version 8 is available as of this writing.

For information about the Netscape browser, go to Starting in October 2004, Netscape shut down its online developer resources. is trying to gain rights to archive and publish those documents.

Netscape Navigator and Communicator 4 was once the king of the browser world. Now its user base has dwindled to a fraction of a percent. Even so, web developers may consider a site's performance in Navigator 4 because it is typical of browsers with minimal support for current standards such as Cascading Style Sheets. Also, web developers can assume that users who still use Netscape 4 really have no alternative, for instance, because it is installed by their organization or is built into an application. While designers generally don't worry about matching layouts exactly in Netscape 4, it is critical that no content gets lost and that advanced CSS or scripting techniques don't crash the browser.

Firefox (previously Firebird) is an open source browser based on Mozilla code. Its popularity exploded in the development community for being small, fast, and highly standards compliant. It also offers features such as tabbed browsing, pop-up blockers, integrated Google search, and better security than Internet Explorer, enabling Firefox to be the first browser to take a bite out of IE's market share. Because it is open source, many useful extensions have been created for it (see the sidebar, "Web Developer Extension for Firefox").

Download and find out more about Firefox at the Mozilla web site,


Created: March 27, 2003
Revised: April 17, 2006