HTML how to tell which elements are visible?

Question

I have seen several solutions which determine when an element is visible in the viewport whilst scrolling the page, but I haven\'t seen any which do this for elements that a

Answer 1

http://www.quirksmode.org/mobile/viewports.html discusses the issues around viewports, determining their dimensions, and calculating element bounds relative to a viewport's coordinate frame. Part 2 of that blog post then goes into the implicit viewports in mobile browsers. He doesn't give code that answers your question exactly, but it's definitely relevant and worth a read.