Simon, if you are sure you changed nothing whatsoever, and if we assume that your site used to work with the same browsers with which it now fails, it must have been your web hoster. For example, they may have switched to newer versions of something.

Such services are very welcome, e.g. for those who want a quick look at the sheet music for ABC postings to Mudcat. However, regular ABC users should run the software on their own computer.

Stanron, have you tried other Windows MIDI software with your Wine? If it works, ask the ABC community. If not, Linux or Wine people may be able to help.