Have your hoster drill down a bit and find the specific rule that is being triggered, then they can remove only that rule, it may be more than one
@AndyJones, try reloading the web server, then search google for "can't use @ in my html on [your_webserver]". Then see if there are any posts about it. Also, I use StackExchange, a lot, to ask questions related to server issues like this. You might consider that. They will be much more knowledgable about issues like this. I'm guessing that you can modify a .conf file and fix it, then reload your webserver without issues.