When a new account is created with cpanel (cpanel11 in my case) some folders and files appear in the root folder (public_html) and mostly people get confused that what are they really meant for? and what are they doing there.
These folders include:
vti_bin
_private
_vti_bin
_vti_log
_vti_pvt
_vti_txt
and a couple of files including:
postinfo.html
.htaccess
Well there is no mystery behind why these files appear, specially in some accounts and not all, the reason behind this is Frontpage extensions. If the account have front page extensions enabled, then there will be these folders in the cpanel account, when a new account is created.
Please note, it is recommended that frontpage extensions should not be turned on until you are really sure that you want to use them.