htcontext: 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/htcontext - from package: tetex-tex4ht

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

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