cssclean: 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/bin/cssclean - from package: dspam-hash

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

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