Rhythms of recurrence explain the meaning of patterns.
Recurrence may bring the reader back to a previously-visited place. For example, many web sites frequently direct the reader back to a central "home page" to ensure that readers are never lost or disoriented. Used judiciously, this hierarchically-motivated recurrence helps readers understand the scope and shape of a web site, although overuse can also create a dull and repetitive experience.
Recurrence may also recall different places without returning directly to them. In this essay, for example, I sometimes use links (see above) that have already been visited simply to remind the reader of an argument already made.
"Breadcrumbs" that mark links as having already been visited, were originally proposed (in Mark Bernstein, "The Bookmark and The Compass", SIGOIS Bulletin 9 (1988) pp. 34-5) as a way to keep readers oriented. Their rhetorical role, as it emerged on the Web, is far richer and more interesting: breadcrumbs remind the reader of what she already knows.