gtkhtml-editor-test: 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/gtkhtml-editor-test - from package: gtkhtml3

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

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