Web Design in a Nutshell, 3rd Edition

Hidden controls are useful for sending information to be processed along with the user-entered data, such as labels used by the script to sort forms. Users cannot see or alter hidden controls. Some scripts require specific hidden fields be added to the form in order to function properly. Here is a hidden element (Figure 15-4):

    <p>This is a hidden element</p>
    <input type="hidden" name="extra_info" value="important" />

Figure 15-4. Hidden input