To block a campaign from bidding on certain websites, follow the steps below:

• Make sure your campaign is set to Targeting: Blacklist in the campaign settings
• Visit the Reporting page and then click Traffic sources
• Select a campaign from the drop down menu
• Toggle the status of the source for that specific campaign

You can also block sources directly from your campaign settings page by entering websites in the targeting box under "Blacklist" mode.

It can take up to 15 minutes for your campaign to stop serving on a specific website after blocking it.