Throughout the environment screen reader specific content is placed off-screen with the CSS class "skip". This is used in many different scenarios, such as <label> elements for input fields, informative text placed in <span> elements, and skip-links used to jump to the main content. All of these elements are positioned off-screen with this "skip" CSS class, however the class itself utilizes the CSS display:none property. This not only hides the content off-screen, but it also hides it from assistive technology. As such, screen reader users never interact with this content.Developers must ensure that screen reader specific content placed off-screen remains exposed to assistive technologies. In order to ensure that this content remains exposed, the CSS display:none property must not be utilized.

Here is additional guidence for invisible content http://webaim.org/techniques/css/invisiblecontent/Many examples of the "skip" class suggest that the should be placed off-screen as opposed to not read. The label a11y:invisiblecontent has been added to track the larger scope of this issue.