553-prohibited file extension

[Helkost]

Hello here. I'm new to this forum, and quite a n00b at FTP programs.

I'm trying to use filezilla and I keep getting this error:

Stato: Avvio upload di C:\Documents and Settings\Helkost\Desktop\phpBB3\viewtopic.php
Comando: CWD /
Risposta: 250 OK. Current directory is /
Comando: PWD
Risposta: 257 "/" is your current location
Comando: TYPE A
Risposta: 200 TYPE is now ASCII
Comando: PASV
Risposta: 227 Entering Passive Mode (208,100,61,2,77,235)
Comando: STOR viewtopic.php
Risposta: 553-Prohibited file extension (.html, .htm or .shtml): viewtopic.php
Risposta: 553 Rename/move failure: No such file or directory
Errore: Errore grave

Can someone explain me ho to fix this? I understood the program doesn't accept the extension .php, but I don't know where to change this setting?
I also have a similar error sometimes (553 Prohibited file name) but I guess the explanation I get for first one would work for second one as well

Thanks in advance for any help you may be able to give me.

H.

EDIT: nvm, I searched better in this forum and found an explanation that fits perfectly: "The server restricts filetypes that can be uploaded. You have to contact the Administrator of this server for help."