Comment: title alone will not make a page understandable - they need to be clear and understandable, and unique (within the site or subsite)
reword 2.4.3, e.g. "Web units have understandable/clear and unique titles."
We have changed SC 2.4.2 (formerly 2.4.3) to "Web pages have descriptive titles" and have also reflected this change in success criterion 2.4.6 (formerly 2.4.5) and support documents for both success criteria.
The success criterion does not require that titles be unique because the working group is concerned that requiring uniqueness will lead to titles that are not as descriptive and usable. It may be very difficult to create titles that are descriptive, unique, and reasonably short. For example, a Web unit that generates titles dynamically based on its content might need to include part of the dynamic content in the title to ensure that it was unique. We are also concerned that authors may make titles unique mechanically, such as by including a unique number in the title that is unrelated to the content. For these reasons, although we encourage unique titles in the techniques for this success criterion, we are not including uniqueness in the success criterion itself.