sslstrip: 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/sslstrip - from package: sslstrip

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

On Debian possible default full paths are:

/usr/bin/sslstrip - from package: sslstrip

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

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