jQuery(window).on('scroll', parallaxScroll);

function parallaxScroll(){

  var scrolled = $(window).scrollTop();

  jQuery('#parallax-lvl-0').css('top',(0-(scrolled*.25)));
  jQuery('#parallax-lvl-1').css('top',(0-(scrolled*.5)));
  jQuery('#parallax-lvl-2').css('top',(0-(scrolled*.75)));
  jQuery('#parallax-lvl-3').css('top',(0-(scrolled*.9)));
}