Validate: 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 CentOS possible default full paths are:

/usr/sbin/validate - from package: mod_auth_shadow

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/Validate - from package: haxml
/usr/bin/Validate - from package: wdg-html-validator

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

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