Official download for Mozilla Firefox 3.0 Simplified Chinese version for Windows:
http://download.mozilla.org/?product=firefox-3.0&os=win&lang=zh-CN
Official download for Mozilla Firefox 3.0 Simplified Chinese version for Mac OS X:
http://download.mozilla.org/?product=firefox-3.0&os=osx&lang=zh-CN
Official download for Mozilla Firefox 3.0 Simplified Chinese version for Linux:
http://download.mozilla.org/?product=firefox-3.0&os=linux&lang=zh-CN
Please do not use download managers, as it may redirect you to RC3.