Made a subdomain, server error

[slycooperfan1]

I've seen the other threads mentioning adding new domains causing server errors, but I have a different, yet most likely related problem. Instead of adding a domain to the control panel, I made a subdomain of my current domain. But that was giving me a server error as well. http://staff.x10hosting.com/default.web.page/

I would love to hear any updates on this from the staff. Thank you guys in advance for the assistance!