Of course, in practice, not all web browsers implement all of the World Wide Web consortium's standards, and not all web browsers implement them correctly. There are always quirks, and it makes sense to test your pages with the most popular browsers in order to iron out any rough edges. Right now, the most important browsers to test are Microsoft Internet Explorer (the most popular), Mozilla Firefox (the second most popular and growing quickly), Safari (standard on new Macintoshes), Netscape 4.x, and the plain text browser Lynx. Testing with Lynx is important because when search engines index your site, they "see" it in much the way text-only browsers do. For more information, see 'how do I promote my web site?'

Although Netscape 4.x and 3.x are still in use by a small percentage of users, we do not recommend limiting your design choices entirely to the feature set of such older browsers. After all, users of those browsers have the option of upgrading to Firefox for free, unless they are using very old computers. We do recommend that you make sure your site is "reasonably useful" with those browsers. Every visitor to your site is a potential customer and deserves your respect.

As of December 2004 on Browser News web browsers stats was as follows:

Browser	Percentage
Internet Explorer 6.x	78%
Internet Explorer 5.x	7.0%
Internet Explorer 4.x	.1%
KHTML based	2.1%
Gecko based	6.6%
Netscape 4	1.1%
Opera	.5%
other	n/a
unidentified	4.9%