vsftpd and create a directory

[Rafnews]

Hi,

i setup a FTP server on our local development server.
So as a developer i can upload and modify websites structure in 
development steps.

everything works well except for 1 thing.

- ftp root is /var/www/html
in this directory i have several other directories like /joomla, 
/magento etc...
in existing directories, i can easily create new subdirectories and files.

however, under the ftp root so under /var/www/html i'm not able to 
create a new directory.
i check the user it is the same as the other directories owner (/joomla, 
/magento, ..)

so what am i doing wrong ?
thx.

A.