uzbl-core: 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/uzbl-core - from package: uzbl

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

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