Any program that can upload to our system using the FTP protocol should work. Our members have successfully used many popular WYSIWYG editors (e.g. Dreamweaver) to create web pages and upload them to our system. Given the swiftly-changing nature of this kind of software, we'd recommend visiting our Member Forum or doing a general search for the latest information.
In addition to regular FTP, we also offer SFTP (Secure FTP) and scp support should you wish to upload your files under the aegis of strong encryption.
Of course, since we offer ssh-secured shell access, you are equally welcome to use vi as your HTML editing tool if you prefer. (Or emacs, pico, nano, and others.)