HI
as per my knowledge

localization testing means.......
now adays every app is dev in any languages,so we can check 
the app in diff languages .

this is WBT testing.

Hi.

  Localization testing is which basically involves the 
translation of web pages into various languages, thereby 
allowing companies to reach a "global public". 

Srini

checking whether our application is supporting the given
local settings like local language,currency,number
systems,date formats etc.. is called localization testing.

It will be tested in both WBT and BBT.

In today's flat world the existence of companies remains
only if it gets edge over its competitor by its product.
Same rule follows in s/w, companies localized there s/w
product in the respective countries native language and then
market it. But localization involves structured approached
while development and in process of localization its
possible some bugs gets mingled with the product.
Localization testing is basically concerned with the testing
of localized product, basically UI and functionlties are
tested. Its black box testing as no code review is done.