I am trying to use Access data in a web application. I get an error trying to navigate to the website once all the precompiled files are up.

First the error message isn't very helpful as it suggests my web.config file has the following setting:
" customErrors mode = "Off" " and suggesting it should be:
" customErrors mode = "RemoteOnly" defaultRedirect = "MyCustomErrorPage.aspx" "

My Web.config file does not have this set to off so why do I get this message?

The real problem I think is the connection string for Access. The obvious problem is I have this in the "value=" section

source=C"\DevelopWebs\.........etc.

I have the access table SWHT.mdf in the App_Data folder under the root of the website. Can I just simply change it to this?
source=\App_Data

I tried this and it didn't fix my problem, so perhaps I have another issue, but need to verify it is OK to set it up this way.
Thanks
Tim