Change history in AdWords allows you to access past revisions made within your AdWords account. This tool can help you track edits made by multiple users, as well as help diagnose changes to traffic patterns or performance.
To access your change history, follow these steps:
Go to Tools and Analysis and choose Change history:
Adjust your date range to reflect your desired dates with the same date selector you use for all other tasks in AdWords.
You have the option to view a graph with traffic and conversion patterns, so you can zero in on specific dates that show spikes or significant dips.
Under Changed by, you can view only the changes made by specific users:
Under Change types, you can select what changes you would like to focus on. The options include:
All
Budget
CPC
Keyword
Status
Distribution
Targeting
Ad
When you click on Show details next to a specific change, you can see additional information, such as what new text ad was created...