Cacti stores certain graph viewing settings for each user, which enables each user to view graphs in an optimal way. These preferences controls things such as the preview graph size or the default graph viewing mode to use. In addition to managing these settings here under user management, each user can change their own settings by clicking on the Graphs tab and selecting the Settings tab on the following page. If you want to prevent a user from being able to keep their own graph preferences, uncheck the Allow this User to Keep Custom Graph Settings checkbox in user management. The user will be presented with an "Access Denied" error message if they attempt to click the Settings tab when this box is checked.