How do modal windows implemented using, for instance, jQuery plugins affect the accessibility of the website? If it leads to poor accessibility, can it be mitigated? Is the only way to avoid using modals at all cost?
For example, people often use TAB to navigate from one control to another. When one shows a modal, like the one in Bootstrap, a user expects that pressing the TAB key will only navigate on controls in the modal. After all, this is how desktop applications on Windows and OS X often behave. Yet, pressing the TAB key will put the focus on other controls and links in the original page. This doesn't seem to be ideal in accessibility terms.
Enabling a screen reader on Bootstrap, then selecting TAB to switch between controls, makes the screen reader "read" text that in effect should really be disabled.
I used several jQuery plugins to implement modals (including Bootstrap from Twitter) and they all seem to suffer from the accessibility issues.