Browser Support for CSS | Page 5 | WebReference

Browser Support for CSS | Page 5

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Browser Support for CSS


One of the earliest graphical browsers was called Netscape. Netscape was the top dog of browsers until Microsoft threw its market dominance around and knocked Netscape out of the competition. The Netscape browser eventually became part of the open source movement, in a project code-named Mozilla.

Mozilla Firefox is an open-source browser developed by the Mozilla Foundation and is available on a wide variety of platforms, including Microsoft Windows, Mac OS X, and Linux and other Unix-like operating systems. The most recent version, as this book is being written, is Firefox 1.5. Firefox provides standard features found on most browsers such as tabbed browsing, pop-up blocking, and good support for user style sheets.

Did you Know?

You can download Firefox for a wide variety of platforms from

Firefox has very good overall CSS 2.1 support, which is one reason why it's used for the screenshots in this book. (The other reason is that it's one of the few current browsers available on all major operating systems, meaning it's very likely that anyone who picks up this book will be able to run Firefox.) There are a few quirks and bugs in Firefox, but in general you won't make big changes to your CSS or HTML to support Firefox users.

By the Way

At the time of this book's writing, a preview version of Firefox 2 is available for testing. Because of the unstable nature of pre-release software, this book doesn't cover any Firefox 2 CSS quirks or bugs.

Other Gecko-Based Browsers

The layout engine used in Firefox is called Gecko, and it has been incorporated into a number of other browsers, some of them open source, and others that are closed but use the layout engine. Because Gecko provides a solid base for CSS implementation, you don't have any extra worries from Gecko-based browsers—no more than those you have for Firefox bugs.

Netscape Browser version 8.1 (, Windows only) is an example of a browser that is Gecko-based—it is proprietary software developed by Netscape Communications (part of America Online), the current owners of the "Netscape" trade name. The user interface shell is closed source, but it uses the Gecko engine. Interestingly, it also can use Internet Explorer's Trident layout engine as well on certain pages.

Making the Gecko family tree even more complicated is the Mozilla browser (, part of the Mozilla Application Suite, which is different from Mozilla Firefox and is currently at version 1.7. Mozilla-thebrowser is now giving way to the open-source project codenamed SeaMonkey, which released version 1.0 ( in January 2006.

The Gecko layout engine is also used on several projects that give a "native" user interface environment, rather than Firefox's more generic, cross-platform user interface. Camino ( is an open-source browser for Mac OS X that feels more like a native Macintosh application, with the Gecko engine doing the HTML and CSS display. K-Meleon ( does the same for the Microsoft Windows operating system, and Epiphany ( is the native Linux and Unix-like browser with a Gecko layout engine foundation.

Other examples of Gecko-based browsers include Flock ( and Galeon (

Older Versions of Netscape

Ancient versions of Netscape—sometimes also called Netscape Navigator and Netscape Communicator, depending on the corporate policy of any given time—had no CSS support; Netscape 3 wouldn't recognize CSS rules or related attributes and elements. This actually made it a good test case for Web developers who wanted to see how their sites would work without style sheets. These days, however, nobody uses Netscape 3 or earlier versions.

Netscape 4 was released in June 1997 and had notoriously bad CSS support. Version 4.02 contained a bug that would cause the entire browser to crash upon reading certain perfectly valid CSS rules. Later versions of Netscape in the 4.x series gradually improved their support for CSS, but even by the release of Netscape 4.8, it was still a very buggy browser that required major work-arounds to do complex CSS layouts.

Fortunately for Web developers, Netscape 4 is all but dead. These days it is used by so few people that there's really little point in using the classic work-arounds and browser hacks for Netscape 4. Unless you are very conscientious, or somehow dealing with a group of primitive users who run Netscape 4 on stone computers, you won't have to make changes to your CSS or HTML to deal with Netscape 4.

Netscape 5 actually wasn't released; the browser developers skipped the numbering to "catch up" to Internet Explorer 6. Netscape 6 was the first Mozilla release, using the new Gecko engine developed by open source developers. The Gecko support for CSS started out strong and has gotten stronger since. In general, there are very few times in which you'll need to use browser hacks to deal with bugs in Netscape 6.2 or later.

Did you Know?

The Netscape website has an incomplete archive of old versions of Netscape for testing. As of early 2006, this appears to be unavailable, but you can find archived versions of Netscape browsers at

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