+1  A: 

In web.config change CustomErrors to Off and callstack to "true" (just search for these values)

Vladi Gubler
actually this is what I did ... please read my question completely
ria
If the error is in one of the Layouts pages, do the same to the web.config located under 14/template/layouts
Vladi Gubler
@ria - if you had actually been clear in your question it may have helped us read it completely!!!
Ryan
http://www.sharepointdevwiki.com/display/public/SharePoint+Development+Debugging
Ryan
@Vladi: thank u so much ... ill just try and then let u know if it worked.@Ryan: thanks for ur comment, but actually I have received answers on this question that means that I was not totally unclear in explaining my query :) anyways thanks for your suggestion
ria
@Vladi: Doing the same in TEMPLATE/LAYOUTS web.config didnt help either. Also note that this web.config didnt have the CallStack attribute as the whole <SharePoint> <SafeControl .. tag was missing.
ria
+1  A: 

You can also see the error in event viewer's Application logs.

sjjoshi
is it the same error which would show up on the aspx page??
ria
It will give you the underlying error.
sjjoshi
+2  A: 

Use the ULS logs. There is even a nice viewer for it too: http://code.msdn.microsoft.com/ULSViewer.

Doug Stalter
ULS Viewer is a great tool and helps troubleshoot SharePoint issues pretty quickly.
Wallace Breza
+1  A: 

It is still possible to make changes to the web.config to get the regular asp.net yellow screen errors. Much like it is with a standard application, the first time you hit F5 in your SharePoint 2010 project, Visual Studio 2010 will prompt you if you want it to automatically configure the local web.config file for you.

However, in SharePoint 2010, the custom error page displays a GUID which can be used as a bookmark in the Log file. It makes searching the Log file much easier. But that GUID will not be displayed on the yellow screen error page, so you might want to take that into consideration before modifying the web.config.

Rich Bennema