hi
You could try using FTP. There are a lot of text editors that have the ability to upload directly to FTP. Also, your operating system may support 'mounting' FTP or WebDAV on your local system as a directory, which would make it as easy as editing a file on your PC. SCP or Rsync on Unix systems is also a good option. What kind of OS do you have, or what exactly do you want?
If you decide to go the route of an simple 'online edit' type script with a web interface, I would make sure to implement some security checks. Especially if this thing will be editing a file on your server's filesystem, or storing the text into a SQL database. Be careful with XSS (wikipedia.org/wiki/Cross-site_scripting) and other things too.