Web Browser Interoperability

If you plan to make extensive use of Linux clients , chances are you'll be using the Firefox web browser ( www.mozilla.org/firefox ) or a relative such as Mozilla that relies on the same core code. The Firefox browser is also available for Windows and, as of this writing, has achieved greater market share than any other alternative to Microsoft Internet Explorer (though still less than 10 percent of the public at large).

A second sometimes significant player is Apple's Safari browser, now the default web browser presented to new users of computers running Apple's MacOS X operating system. The Safari project shares much of its development with Konqueror, the second most common Linux browser. And Microsoft Internet Explorer, of course, is still used by the vast majority of the public as of this writing. Meanwhile, slightly less than 1 percent of users still use the severely outdated Netscape 4. x browser.

So what does this mean for the interoperability of our websites? For publicly accessible websites , there are three major players to concern ourselves with: Mozilla/Firefox, Konqueror/Safari, and Microsoft Internet Explorer. That means we have at least three major browsers to thoroughly test our publicly accessible web pages with.

Note 

There are exceptions. Other independent browsers, like Opera ( www.opera.com ), should also be tested if you know you'll be using them.

But advanced browser compatibility issues for publicly accessible websites are a bit beyond the scope of this book. We're primarily concerned here with issues that arise when an organization chooses to use Linux and Windows clients together internally .

Firefox is freely available for all Linux distributions, highly compatible with Internet Explorer, and standard in Fedora. So we'll simplify things by eliminating Konqueror/Safari from consideration. For the purposes of this book, Firefox is the standard Linux browser and Internet Explorer is the standard Windows browser. When we refer to "both browsers," we are referring to Firefox and Internet Explorer. Of course, Firefox for Windows behaves almost identically to Firefox for Linux, so most comments regarding Firefox apply equally on Windows. Indeed, standardizing on Firefox on both platforms may be an attractive option for some organizations.

For the most part, the two major web browsers are now highly compatible with one another. Internet Explorer and Firefox both implement open standards, and Firefox strives to implement lesser-known and unofficial features of Internet Explorer as well, with a great deal of success. Today, Web pages that adhere to the HTML 4.01 standard will typically render well on both browsers. Therefore we recommend validating your pages for compliance with HTML 4.01 or XHTML 1.0.

But there's one big catch: the use of plug-ins and helper applications that are not typically installed on Linux or, worse , not available at all.

Plug-ins are not the best way to develop content for the Web, unless the content you are creating simply cannot be expressed using the open standards mentioned earlier in this chapter. When you do have to use plug-ins, never use obscure or platform-specific plug-ins. For most applications, nonstandard formats simply are not necessary to implement the design you want. However, if you must use nonstandard formats, restrict yourself to those that are widely used and for which plug-ins or helper applications exist on many operating systems.

These "friendly" formats include Adobe's Portable Document Format (PDF) for printable forms and other printer-friendly documents, Macromedia's Flash (but not Shockwave!) format for interactive animations and games , Sun's Java plug-in for interactive miniature applications or applets , and RealNetworks's RealAudio and RealVideo for web-optimized audio and video. Plug-ins for these are available free of charge for both Windows and Linux, as well as MacOS. Alternatively, MPEG Level 2 video and MP3 audio make good "common denominator" choices because they are supported by all of the major audio and video plug-ins and helper applications.

However, the plug-ins for most of these formats are not included directly with Fedora Core 3, although they are included with some non-free Linux distributions. In most cases, this is because the license terms attached to the plug-ins allow free distribution only from the website of the company that produces the plug-in. An exception is PDF: Fedora Linux includes an open-source PDF viewer as standard equipment. Even here, though, the official Adobe version does have worthwhile extra features like support for the "fill-in form" feature.

How can we install support for the plug-ins we need on the Linux platform to bring it closer to par with Internet Explorer's support for these file formats? Space prevents us from presenting every plug-in and helper application in detail. However, the Mozilla/Firefox project maintains an excellent page that provides pointers and instructions on installing each of the important plug-ins available for Linux. You can find that page here:

• http://plugindoc.mozdev.org/linux.html

Another fine resource for this is Stanton Finley's excellent and frequently updated "Fedora Core 3 Installation Notes," which you can find here:

• http://stanton-finley.net/fedora_core_3_installation_notes.html

Finley's page includes information about the use of alternative Fedora package repositories to make the process somewhat more automatic for some plug-ins. Unfortunately, in some cases, license terms rule out installing the plug-in automatically and the manufacturer's installation scripts must be used.

We recommend installing plug-ins and helper applications on every Linux client for Flash and Java. We also recommend installing RealPlayer to provide support for the major open audio and video formats as well as its own proprietary audio and video formats.