Switching localization in Iceweasel & Icedove

[Anton Liaukevich <anthonyl@uvaga.by>]

I use Debian Lenny. I had installed iceweasel & icedove packages with 
corresponding localization packages for russian and belarussian 
languages (iceweasel-l10n-ru, iceweasel-l10n-be, icedove-l10n-ru, 
icedove-l10n-be).

Both languages are visible in Add-ons windows of Iceweasel & Icedove. 
But I don't know how to select language that I want to Iceweasel & 
Icedove have. Help me, please.

My software:
    kde-core: 5:48
    iceweasel: 3.0.1-1
    iceweasel-l10n-ru: 1:3.0.1+debian-1
    iceweasel-l10n-be: 1:3.0.1+debian-1
    icedove: 2.0.0.14-1
    icedove-l10n-ru: 1:2.0.0.14+debian-1
    icedove-l10n-be: 1:2.0.0.14+debian-1