This page tests whether a click event propagates with the correct target and positioning. See rdar://problem/4477126.

click inside the red box:
[]
PASS: event target should be [object HTMLSpanElement] and is
PASS: event.pageX should be 175 and is
PASS: event.pageY should be 105 and is
PASS: event.clientX should be 175 and is
PASS: event.clientY should be 105 and is
PASS: event.layerX should be 7 and is
PASS: event.layerY should be 5 and is
PASS: event.offsetX should be 7 and is
PASS: event.offsetY should be 5 and is
PASS: event.x should be 175 and is
PASS: event.y should be 105 and is