ThickBox is a webpage UI dialog widget written in JavaScript on top of the jQuery library. Its function is to show a single image, multiple images, inline content, iframed content, or content served through AJAX in a hybrid modal.
Thickbox shows a UI dialog widget, which remains centered on the page. It's like a jQuery dialog box, but it has an added functionality of remaining centered even after scrolling.
It comes with its own set of CSS files for styling of the box.
Thickbox is now deprecated in favour of jQuery, having its own dialog box and other UI components with the jQuery UI library.