csscompress: 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/csscompress - from package: dspam-hash

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

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