Sometimes anti virus will claim a website is unsafe based on reports. It could be the simple cookies used to login that it may consider unsafe. It could be that someone has shared a file here in the past that resulted in a virus, and the anti-virus company may have been notified or noticed it.
This site doesn't have any advertisements on it as far as I know, so theirs no direct third party code that appears that could be malicious.
I highly doubt this website has any vulnerabilities/viruses, however sometimes when people add code to their websites, plugins, or something like that, it can be infected with code that could jeopardize the entire web server if the software/code they are adding came from an unreliable source.
If you could share more information it might help the techies..
- Have you received any error codes or specific messages you could share to help identify the source?
- What Anti-virus do you use?
- When did you first notice this?