gistfile1.js

$("li .active span", '#list').each(bindEvenToSpan);

function bindEvenToSpan(i, elem) {
  var $this = $(elem);
  
  if($this.hasClass('shouldReact')) {
    $this.on('mouseenter', addCssToSpan);
  }
}

function addCssToSpan() {
  var $this = $(this),
    content = $this.data('newcontent');

  $this.css({
    border:'1px solid #cccccc',
    backgroundImage: 'url("/newbg.png") 10px 36px no-repeat',
  }).html(content);
  
  // persnally i would just create a new class and add the class to the element instead of add the inline css
  // $this.addClass('superstar');
}

gistfile2.css

.superstar {
  background: url("/newbg.png") 10px 36px no-repeat;
  border: 1px solid #cccccc;
}