Site keeps going down – Error '500'

When I try and access my web site http://cloudbestpractices.net, I keep getting a failure page, that says:

“The cloudbestpractices.net page isn’t working

cloudbestpractices.net is currently unable to handle this request.

500″

I contacted my web host who said it was working fine at their end and for me to clear my cache etc. I tried that and am also checking from another location, but same problem.

Can you shed any light on where this error is occurring please?

thanks, Neil.