Browser Compatibility


Testing is obviously important in the development of any website. When considering accessibility in a low bandwidth environment, it becomes especially important to consider what features may or may not be available to users. CSS, JavaScript and HTTP compression support are all browser dependent, with the normal rule being that the older the browser is, the less accurately it will implement standards. If you have implemented HTTP compression and used CSS to lay out your site, as suggested, then it's worth checking that browsers are showing what you intended. It's also worth checking that the site is still usable with CSS support and JavaScript turned off, assuming that your browser supports this.

Choosing Browsers to Test Against

We strongly recommend that you test your websites with at least Internet Explorer 6 and 7 and Firefox 2. At the time of writing, these three browsers account for over 90% of the market.

Firefox is stricter in its support of web standards than Explorer, and some code that is not standards-compliant will work in Internet Explorer but not in Firefox. Identifying and fixing such code will help to ensure that your site conforms to standards, making it more likely to be compatible with any given browser.

If possible, we recommend that you test your site against other browsers: Opera, Safari, Internet Explorer 5, Firefox 1.5 and Konqueror which all have a small share of the browser usage market, and additionally older browsers such as Netscape 4 and Lynx. Testing with Netscape 4 and Lynx ensures that your site is accessible to browsers with very basic functionality, which increases the likelihood that it will work with any given browser, for example proprietary browsers used by mobile devices.

You can download all of these browsers free for Windows, Unix and MacOS X:

Browser Windows Unix-like (e.g. Ubuntu Linux) MacOS X
Opera 9
Safari/Konqueror Safari 3 Beta Safari 3 Beta
Netscape Navigator 4.08 Communicator 4.8 Navigator 4.08
Lynx Lynx on Windows
Internet Explorer Multiple versions of IE (3, 4.01, 5, 5.5 and 6) on one machine
Alpha version of a test tool for IE 8 beta 1, 7, 6, and 5.5 on Windows Vista and XP
Official Microsoft site
IEs4Linux IEs4Linux - Mac
Running Internet Explorer on a virtual machine


  • Test websites with at least Internet Explore 6 and 7 and Firefox 2
  • Check how HTTP compression affects the components of your site in different browsers
  • Check usability of your site when CSS and JavaScript are disabled