title: Content with 100% between header and footer
body: <p>Lets assume I have the following layout (see image below)... I have a header (A) at the top, footer (C) that is always at the bottom and container (B) that is in the middle and should fill the space left between the header and the footer by 100%.</p>
  
  <p><img src="https://i.stack.imgur.com/vyvOc.png" alt="enter image description here"></p>
  
  <p>Can't think of any way how to achieve this using pure css. Any ideas would be appreciated!</p>