1. Select Preferences from the Safari menu or hold down the Command key and the Comma key at the same time (Command+,)
2. Go to the Privacy tab.
3. To remove stored data by site, click the Manage Website Date… button.
4. Select the sites with stored data you want to remove. Hold down the Command key to select multiple sites. Click Remove.
5. Click Done.
Alternatively, you can click the Remove All button to delete all of the sites' cookies and stored data. Safari will ask you to confirm your choice: