Here’s an old bit of code that I found to position something centrally inside an element.

  1. #idOfTheDiv {
  2.    width: 400px; /* here you put the width that you need */
  3.    height: 200px; /* here you put the height that you need */
  4.    position:absolute;
  5.    left:50%;
  6.    top:50%;
  7.    margin-left:-200px; /* this number always to be the width divided two in negative */
  8.    margin-top:-100px; /* this number always to be the height divided two in negative */
  9. }