Though modal dialogs are not a new concept in UI design, the number of homegrown  Lightbox clones ( source) appearing on the Web since major JavaScript libraries like Prototype and jQuery hit the scene has been staggering. Unfortunately, many of the clones developed leave some key usability considerations unaddressed, and struggle with common problems in accessibility.

Some key usability features that should be considered during creation of a Web-based modal dialog include (1) manage focus and allow tab navigation (2) disable elements outside the modal dialog (3) give users an out and (4) provide graceful error recovery.