manweb: 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/manweb - from package: netpbm-progs

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

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