Not responding to Web application

I am trying to run my webapplication using twitter. It is redirecting to my application but not responding. Showing server error'/' application - runtime error. But my problem is that i cant view the error details because the current custom error settings for my application prevent the details of the application error from being开发者_Go百科 viewed remotely. However to view the error details i created a tag with its "mode" attribute set to "Off" within the "web.config" configuration file located in the root directory of the current web application. But still its not showing me the error details. Please help.

This usually means the error is happening before the application has started or there is an error in the web.config (i.e. invalid xml, unknown tags ... etc)