dwm.web: command not found

Have You tried accessing the binary with the full path?

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 Debian possible default full paths are:

/usr/bin/dwm.web - from package: dwm

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