csslint: 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/csslint - from package: csslint

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

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