Configuring FBA might generates "Unknown Error"

After configuring FBA for an extranet site. I always get “Unknownerror” when I try to sing in. the steps followed are described here :

https://devcow.com/blogs/jdattis/archive/2007/02/23/Office\_SharePoint\_Server\_2007\_Forms\_Based\_Authentication\_FBA\_Walkthrough\_Part\_1.aspx

solution :

1-    check for the application poolidentity that host the extranet site.

2-    Goto SQL Server to your FBAdatabase created

3-    Give put the app pool identityaccount in dbo role. Make sure to put there. It is not enough to map it to dboschema as a default schema

You can detect this error in MOSS logs under : C:\ProgramFiles\Common Files\Microsoft Shared\web server extensions\12\LOGS