title: Set margin-top to a % of the parent element's height
body: <p>I want an element's margin-top to be a % of the parent elements height.</p>
  
  <p>For example if I have div that has height 100px, I want to create a p element inside of it that has margin-top: 25px, except by setting the p element's margin with % so it can handle its parent changing height. </p>
  
  <p>Edit: For those that think this is obvious - you can't use margin-top: 25%. %'s for the box model except height use the parent element's width. So you are setting it to 25% of the parent div's width if you use margin-top: 25%. </p>