XF 1.3 can no longer edit EXTRA.CSS

Every time I try to add to my EXTRA.CSS it throws up this error, so I reverted the template and now it will not let me put any code in!

here is the error:


can anyone help?


XenForo moderator
Staff member
That appears to be an error message generated by the server.
It's possible that mod security is blocking something, as the text at the bottom indicates.

Contact your host and explain the problem.
They should be able to help.
oddly I just logged into my server and under Modsecurity I have 3 settings

2 detect mode
3 not active

switched to detect mode and it started to work again!
odd as it has been working fine for months!