Fieldsets, Legends and Screen Readers
http://www.paciellogroup.com/blog/?p=3

Lemon, Gez
Paciello Group, The
2007

Abstract:

The grouping and labelling of thematically related controls within a form is an important aspect of providing semantic information so users can understand and complete a form successfully. Differences in quality and implementation of support across user agents can hamper some users' ability to benefit from this information. This must not be taken as disincentive to developers, as the benefits of using these elements outweighs the negatives. But it is clear that some assistive technology vendors need to improve implementation of HTML features that enhance accessibility, so their users can gain the most benefit.