Whoops! There was an error in Laravel-4 Startup

Suddenly When I tried to reach laravel 4 Documentation on my server ,a strange colorful screen came out  saying  :

"Whoops! There was an error"

This is a debug stack trace detailed page taking from Symfony Package which is used with laravel packages as  an error stack trace  display script .
(Sorry.. Laravel-4 going to be elites software not for anyone , and I think it will lose its popularity )

Ok. How to solve this issue , As I said this is a detailed information about the error you got,If you are lost in these crowded tech information then you can reach the single line error page by changing the variable debug value from True to False in the configuration file app.php.
You can find this file in app/config/ folder .
After changing the value  to false regenerate the error again and you will get a single line error telling you what is the problem.