How can I backup from a HTTP web server?

SyncBack cannot directly download files from a HTTP server, but can use FTP. If FTP is not an option then a 3rd party program could be used in the Run Before setting of a profiles configuration to download the files to the local drive. Those files could then be copied to their actual destination, e.g. an FTP server, Zip file, etc. Freeware such as curlĀ can be used to download files via HTTP:

https://curl.haxx.se/docs/httpscripting.html