It looks like a legitimate error screen. Certainly, an admin from the beemaster site could confirm the existence of the page. Another thing that makes it look real, is the IP address it is reporting in error message. It belongs to a router that appears to belong to Invisalink.net. ISPs are constantly being barraged by people trying to hack into them, so it's possible that the router was compromised in some way.
That said, it's good that you stopped at that point and questioned the validity of the page. Many people just click through pages that appear to be legitimate, giving away personal information along the way, and end up having their identities compromised or stolen.
Also, keep your browser and antivirus\spyware current. There are anti-phishing and anti-malware tools built into them that you can use to help validate a web page.