HTML and CSS Reference
hierarchical table of contents and summary of each act linked to appropriate places
within the text, similar to what is shown in Figure 2.12.
Because this structure is both linear and hierarchical, you provide links to go forward
and backward, and links to return to the beginning and to move up in the hierarchy. But
what is the context for going up?
If you've just come down into this page from an act summary, the context makes sense:
Up means go back to the summary from which you just came.
But suppose that you go down from a summary and then go forward, crossing an act
boundary (say from Act 1 to Act 2). Now what does up mean? The fact that you're mov-
ing up to a page you might not have seen before could be disorienting given the nature of
what you expect from a hierarchy. Up and down are supposed to be consistent.
Consider two possible solutions:
Do not allow forward and back links across hierarchical boundaries. In this case, to
read from Act 1 to Act 2 in Macbeth , you have to move up in the hierarchy and
then back down into Act 2.
Provide more context in the link text. Rather than just Up or an icon for the link
that moves up in the hierarchy, include a description of where the user is moving to.
A web is a set of documents with little or no actual overall structure; the only thing tying
each page together is a link (see Figure 2.13). Visitors drift from document to document,
following the links around.