Screen Readers and 'display:none'
http://juicystudio.com/article/screen-readers-display-none.php

Lemon, Gez
Juicy Studio
2007

Abstract:

When an element is hidden with display: none, the browser doesn't generate a box for the element; the element is not visible on the screen, and the layout of the page isn't effected by the element. As screen readers are supposed to read the screen, it makes sense that they do not announce content that is hidden with display: none.