Internet Explorer 6.0

Internet Explorer 6.0 is the standard browser in the latest version of Windows (Windows XP). It was released in August 2001.

Windows XP is built on Windows 2000 and is the successor to Windows 98, Millennium, and Windows 2000.
Internet Explorer 6.0 for Windows 98, Windows Millennium, Windows NT and Windows 2000 can be downloaded from Microsoft's Internet Explorer site:
http://www.microsoft.com/windows/ie/default.asp

Internet Explorer 6.0 is the most commonly used browser today.

Internet Explorer 5.5

Internet Explorer 5 was the first major browser with XML support.
Version 5.5  (July 2000) for Windows 95, 98, NT 4.0, and Windows 2000.
Contains better support for XML/XSL, CSS, printing (print preview) and HTC behaviors.

Mozilla

Browsers based on Mozilla code (Mozilla, Firefox, & Camino) is the second  largest browser family on the Internet today, representing about 20% of the  Internet community. Mozilla browsers are known to have very  good web  standards support.
http://www.mozilla.org

Safari

the Mac OS X default web browser, offers you a superior web experience with outstanding performance. Even the most complex of pages load at breakneck speed. In fact, Safari loads pages more quickly than any other Mac web browser. But thats not all. Safari uses the advanced interface technologies underlying Mac OS X to offer you an all-new view of the web, one thats much easier to use.