refs #4996 started to work on detecting whether an element is visible or not. This is quite a complex task and I do not think it can always work 100%. There are too many factors and ways to hide an element. For instance using a zIndex, zoom level, when a div is scrollable, CSS might not be applied yet at the time we scan etc. So far this should cover most cases but it must be clear it cannot work in all and there still needs to be a lot of testing. Also need to detect whether CSS was applied or not