Salesforce allows each user to customize his or her display, including control of which tabs are turned on and which related lists are displayed on each detail page.
For Professional Edition, display customization is a user-specific setting. There is no way for an administrator to turn tabs on or off for all users at once.
If you are a System Administrator, you can forward these instructions to your users to have them turn Tabs on or off:
1. Log into Salesforce.
2. Click on:
Setup | Personal Setup | My Personal Information | Change My
Display |Customize My Tabs.
3. Select the desired tab from the selected tabs or available tabs list.
4. Click remove or add to move the tab to the available tabs list or
selected tabs list.
5. Click "Save".
For Enterprise Edition, custom profiles can control which tabs appear. To customize an existing custom profile and hide or turn off tabs, follow these steps.
1. Click on:
Setup | Administration Setup | Manage Users | Profiles.
2. Click the edit link to the left of the custom profile.
3. In the tab settings area, select the appropriate value from the picklist.
The following choices affect tab visibility.
1. Default On: Show the tab by default for users with this profile.
Individual users can override this setting for their login.
2. Default Off: Hide the tab by default for users with this profile.
Individual users can override this setting.
3. Tab Hidden: Hide the tab and do not allow individual users to
override this setting in their personal customization.
Please note that this settings apply to the Original Profile Interface. To know more about the Original and the Enhanced interface please visit Working with Profiles in the Original Profile Interface and Enhanced Profile User Interface Overview