title: How to set DIVs so that the page vertically fits the screen?
body: <p>This is the structure of a page.</p>
  <p><img src="https://i.stack.imgur.com/cu1wA.png" alt="enter image description here" /></p>
  <p>the height of <code>header</code>, <code>menu</code> and <code>footer</code> is known (fixed and set by pixels) but the <code>body</code> height is not. but I want it to be so height such that the site completely covers the screen vertically. I mean I need to set a <code>min-height</code> for the <code>body</code> that causes the page fits the screen. how can I do that?</p>