iceweasel: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/iceweasel - from package: iceweasel

You may install the required package with command apt-get install {package}

Error in other languages:
iceweasel: bevel nie gevind nie
iceweasel: comandă negăsită
iceweasel: comando não encontrado
iceweasel: commande introuvable
iceweasel: command not found
iceweasel: käsku ei ole
iceweasel: không tìm thấy lệnh
iceweasel: komanda nerasta
iceweasel: Kommando nicht gefunden.
iceweasel: kommandot finns inte
iceweasel: komut yok
iceweasel: nie znaleziono polecenia
iceweasel: níor aimsíodh an t-ordú
iceweasel: no se encontró la orden
iceweasel: no s'ha trobat l'ordre
iceweasel: opdracht niet gevonden
iceweasel: parancs nem található
iceweasel: perintah tidak ditemukan
iceweasel: príkaz nenájdený
iceweasel: příkaz nenalezen
iceweasel: команда не найдена
iceweasel: командата не е открита
iceweasel: 命令找不到
iceweasel: コマンドが見つかりません