Screen Readers
Screen readers run on top of browsers and retrieve the data from the browser, meaning that when a browser that supports JavaScript encounters a script, it will try to execute it; this may potentially cause problems for users, because they may not be aware that something is happening. Screen readers only offer linear access to a page, so if a script changes something located above the content currently being read, the user won't have any way of knowing about it.
Further complicating the issue is the fact that each brand of screen reader handles JavaScript events differently – an event that works with one brand of screen reader might not work with another – or even an older version of the same brand.
It has been suggested that screen reader users disable JavaScript in their browsers. This is not the best solution; but, at present, it is probably the only thing that can be done. Also keep in mind that this applies only to screen-reader users; people with other disabilities should still be considered; asking all of them to disable JavaScript isn't necessary when it is possible to create accessible JavaScript for them.