SharePoint Error message Full descriptive

SharePoint developers and Administrators sometimes will may get the error message as "An unexpected error has occurred"

By default SharePoint 2010 did not return a descriptive error message.
For displaying error message description you need to turn on Error Message.

Here are the steps for turning on the error messages instead of "An unexpected error has occurred"

1. Open IIS--> and right click on the site and select explorer.
2. Find web.config filen right click on it and select open with notepad.
3. Find this line "<SafeMode MaxControls="200" CallStack="false" DirectFileDependencies="10" TotalFileDependencies="50" AllowPageLevelTrace="false">"
4. Change both "CallStack" and "AllowPageLevelTrace" from false to true.
5. Find the line "<customErrors mode="On" />" and change the mode from On to Off.

Now you will be able to see the error message with complete details.
You can get the error message description from Errors Event ID in Even Viewer.
And you can get all the information about error message in URL Logs in C:\...14\LOGS folder.