I'm not familiar with the error you listed, but it does sound like a permissions problem. Each directory/file in *nix has permissions attached to it, and user mark doesn't have permission to create files in /var/www/html. The easiest solution (that is also safe) is to ftp the files into /home/mark/, and then use sudo or su to move the files into /var/www/html. You could also change the permissions on /var/www/html/, but that would make a real world webserver unsecure. As you plan to use this to learn, it is best to use the box as a real world server would be, and allowing easy access to the web directory is not the best of ideas. That will make it a 2 step process, the ftp step, then use putty or whatever your ssh client is to move the files. Many web developers like a program called SCP or something like that, which is just a port of the *nix scp (secure copy) program for Window$.
You could also change the permissions to allow mark to write to the directory, or ftp as root, but I don't think most ftp servers will allow root to log in. The ftp server I use, vsftp doesn't allow that at all, unless you modify the .conf file.