Deleting AutoFill information
If Safari is set to automatically fill in forms for you, you can turn off this feature and delete any information Safari has stored.
To turn off AutoFill and delete saved information:
Choose Action menu > Preferences and choose AutoFill. (The Action menu is near the upper-right corner of the Safari window, and looks like a gear.)
Deselect “Using info from my Address Book card” and “Other forms.”
Next to “Other forms,” click Edit. A list of websites where you normally fill in information such as your name and email address appears.
Select individual websites and click Remove, or click Remove All. Click Done.
The Edit button next to “Using info from my Address Book card” opens your address book. You probably don’t want to delete the information that’s on your address book card because it’s used in applications other than Safari.