Is HTML text string within current scrolling visible area of browser window?

[Keith Clarke]

Hi folks,
Can anyone help me with the correct terms to seed my Google search? 

I'm trying to discover whether it's possible to check programmatically (maybe with Javascript, Jquery, etc.) whether a specific element on a web page (that is readable from the page HTML), such as a specific div, tag or string, is currently within the visible rendered page area of a browser window with a (vertical) scroll bar.

Otherwise, if it's a specific page - with a known layout and therefore calculable coordinates for the element to find - is it possible to know how the browser window's current size and scroll offset relate to the 'underlying' page?
TIA,
Keith..