error "cannot create remote file"

i try to copy file from winxp to ubutun 7.10 /var/www and i got this error message but if i copy from xp to /home/administrator/web the files are successfully copy. Why is this happen?
Another question, i can't copy from /home/administrator/web to /var/www. Why?

It sounds like you do not have write permissions to the directory where you're trying to put the file. You will need to log in as a user who does have write permissions for that directory.