FastClick is instantiated on the body element, so all visible elements on this page will receive fast clicks - except one.

The layers marked A and B both have click handlers that will attempt to trigger focus on the input element programatically. However, on iOS before version 5.0, touch event handlers are not allowed to trigger focus on other elements.

On earlier versions of iOS, only B will succeed at triggering focus on the input element, because it has a needsclick class which will instruct FastClick not to trigger a programmatic click in the touch event handler and let the system click event go through instead.