Use of View Setup Audit Trail
Using View Setup Audit Trail
Setup > Administration Setup > Security Controls > View Setup Audit Trail
The last 20 entries for your organization are listed. You can download your organization’s setup audit trail for the last six months (Excel .csv file).
The setup audit trail history shows you the 20 most recent setup changes made to your organization. It lists the date of the change, who made it, and what the change was. Additionally, if a delegate (such as an administrator or customer support representative) makes a setup change on behalf of an end-user, the Delegate User column shows the delegate’s username. For example, if a user grants login access to an administrator and the administrator makes a setup change, the administrator’s username is listed.
The setup audit trail history tracks the following types of changes:
Administration, Customization, Security and Sharing, Data Management, Development, Various Setup and Using the application.
Source : https://cs13.salesforce.com/help/doc/user_ed.jsp?loc=help&target=admin_monitorsetup.htm§ion=Security