One is the version Firefox 1.5.

Links:

Info: http://www.mozilla.com/firefox/

Mac: Http://releases.mozilla.org/pub/mozilla.org/firefox/releases/1.5/mac/es-ES/

Windows: Http://releases.mozilla.org/pub/mozilla.org/firefox/releases/1.5/win32/es-ES/

Linux: Http://releases.mozilla.org/pub/mozilla.org/firefox/releases/1.5/linux-i686/es-ES/