title: Scrollable container in webpage
body: <p>I want to create a viewport inside a webpage with scrollbars.</p>
  
  <p>In this viewport I want to place a collage of images at arbitrary offsets relative to each other.</p>
  
  <p>The first image I add should be centred in the viewport.  It may not be as big as the viewport.</p>
  
  <p>As other images are added over time, they are some polar coordinates from some other image.  I can turn polar coordinates into X Y offsets.</p>
  
  <p>As I add images, I may want them to be left of all other images or above all other images and so on; can I use negative offsets?  Can the scrollbars on the viewport scroll over the used coordinate range of the children automatically, rather than being from 0,0?</p>
  
  <p>What container class with which CSS settings do I use for the viewport?  What CSS position settings do I use to position the children?</p>