Guideline 3.2: Make Web pages appear and operate in predictable ways.
This guideline ensures that before a user takes any action on a web page, it can be expected how the particular page will behave. This means that pages either behave conventionally, or when the behavior is by default unexpected, warnings and instructions are provided to the user beforehand.
3.2.1: On Focus (Level A)
When any component receives focus, it does not initiate a change of context. (Level A)
When the user switches the focus to another element, this focus should remain there until the user decides to proceed, as well as it should not change the content related to the focused content.
This success criterion is not a limitation of web 2.0 applications. The page content is allowed to change based on user interaction.
What's important here is that the user is in total control of navigating among elements. An example would be that based on a country selection, the state/province list will update. When the user, for example, selects Canada, it is allowed to update the following list from U.S. states to Canadian provinces, as long as the focus remains in the country list. Do not assume that a selection means that the user is done choosing, the selection is made when the user leaves the field where the selection takes place.
Also, as the user switches focus among elements or makes a selection, do not switch the focus to a different screen or window. Allow the user to indicate to be ready for the next step by activating "OK", "Go", "Next", etc.
3.2.2: On Input (Level A)
Changing the setting of any user interface component does not automatically cause a change of context unless the user has been advised of the behavior before using the component. (Level A)
It maybe necessary to change the context based on the user selection. However, when this is necessary, provide a warning to the user in the given context on how the context is going to change when the user changes the input. This could, for example be harmful when the user already made a selection and entered information, but changing a setting will disable the already entered information. In this case, when the user decides to revert to the previous setting, the already entered information is lost.
3.2.3: Consistent Navigation (Level AA)
Navigational mechanisms that are repeated on multiple Web pages within a set of Web pages occur in the same relative order each time they are repeated, unless a change is initiated by the user. (Level AA)
When the same navigation features are used throughout several pages, ensure that this navigation occurs in the same order. For example, do not change the layout or the location of a menu. It is, however, allowed to include a submenu when activating an item on the main menu.
You can change the order of navigational elements, however, allow the user to initiate this change.
3.2.4: Consistent Identification (Level AA)
Components that have the same functionality within a set of Web pages are identified consistently. (Level AA)
When you refer to a particular section of a web page, or to a functionality, make sure you use the same reference. For example, do not use two different images to identify the same functionality.
3.2.5: Change on Request (Level AAA)
Changes of context are initiated only by user request or a mechanism is available to turn off such changes. (Level AAA)
This success criterion is related to 3.2.2, but the difference is that instead of warning the user when a change will occur, do not make any changes to the context of an element without the users confirmation. When you would like to offer automatic changes, provide an alternative option which the user can select to receive warnings about changes. An example would be a complex form when based on user input the content of other fields will change. You can provide an alternative of this form in several steps where the user has to fill in a fewer number of fields, and confirm to proceed to other fields where the changed content would appear.