$(function() {
  
  $(window).resize(function() {
    
    var screenCenterX, screenCenterY, elementCenterX, elementCenterY, $element, topPos, leftPos;

    $element = $('.content');

    screenCenterX = $(window).width() / 2;
    screenCenterY = $(window).height() / 2;
    
    elementCenterX = $element.width() / 2;
    elementCenterY = $element.height() / 2;

    leftPos = (screenCenterX - elementCenterX > 0 ? screenCenterX - elementCenterX : 0);
    topPos = (screenCenterY - elementCenterY > 0 ? screenCenterY - elementCenterY : 0);

    $element.css({top: topPos, left: leftPos});
    
  });
  
  $(window).resize();
  
});