encoded url

Currently I access a Taiwan Site with Chinese URL by Firefox Chinese 4.x version and it does not display correctly. After compare URL between 3.x and 4.x, the root issue is that 4.x convert Chinese Characters as UTF8. By the way, Firefox 4.x English version is OK. Could anyone help solve this issue ? Fire 3.x: http://help1.ssl.cc.tw1.yahoo.com/frame_sub_category.html?skip=1&prodid=10&catyname=%A5%E6%A9%F6%A7%B9%A6%A8%B6%B7%AA%BE&funclass=%ABH%A5%CE%B5%FB%AF%C5 Fire 4.x: http://help1.ssl.cc.tw1.yahoo.com/frame_sub_category.html?skip=1&prodid=10&catyname=%E4%BA%A4%E6%98%93%E5%AE%8C%E6%88%90%E9%A0%88%E7%9F%A5&funclass=%E4%BF%A1%E7%94%A8%E8%A9%95%E7%B4%9A