This shows that there is a error somewhere in your rails application. More details about this error can be seen in two ways. They are as follows,
1) Login into your control panel and refer the Error log section.
2) Follow this path :- RAILS_APP/log/
Genrally you will get more appropriate information if you refer rails log directory. There are different files which are stored in there and it will depend upon the mode that you selected while you logged in. While using FastCGI wrapper, fastcgi.crash.log is needed. While regular CGI, it’s a type of log between many others, depending on the mode you’re in. Genral errors are incorrect database settings and bugs in your code.