used to display large images using modal dialogs
Lightbox is a JavaScript technique used to display large images using modal dialogs. The effect has gained widespread popularity due to its simple yet elegant style and easy implementation. Some of the first implementations did not use any libraries, many now use a number of JavaScript libraries in order to reduce the size of the code.
Questions having the lightbox tag regards the User Experience of lightbox.
Reference: http://en.wikipedia.org/wiki/Lightbox_(JavaScript)
