在theme_breadcrumb()中增加了无形的标题.

(Issue)

In D6 there is no markup to indicate the role or purpose of the breadcrumb links to users of screen-readers.

Drupal 7 provides a heading before the list of breadcrumb links, which is visible to screen-reader users and when CSS is disabled. This heading has been added to theme_breadcrumb() and to garland_breadcrumb().

<h2 class="element-invisible">You are here</h2>