Some websites not displaying japanese correct

Hello people,

so I can surf lots of sites in japanese, and all symbols are shown correctly. But there are also some sites where the symbols are not shown correctly.
Compare "只今リニューアル中" (Oh I hope it'll display properly here :p) for example, with "B`ƒnƒKƒNƒŒ`)ƒZƒb".
 Could someone please explain this, and tell me if I could solve this somehow . Thanks

Windows XP, Firefox

I tried with Internet Explorer too, same thing there. I find it strange since some other websites displays perfectly.

Like this site for example:
http://sim-kengo.hp.infoseek.co.jp/build4/hokuya.html
Looks like "’ljÁ•û–@F—·‹q‰w‚Æ‚µ‚ĒljÁŽû—el”F6000lÝ’u”ï—pF˜200“P‹Ž”ï—pF§150", while this site displays perfect:
http://moritetsu.web.infoseek.co.jp/