Хм, я люблю использовать Traversal API 
 
  
 
<span>Текст1</span>
<span>Текст2</span>
<span>Текст3</span>
<span>Текст4</span>
<span>Текст5</span>
<script type='text/javascript'>
function load(){
 function spanFilter(n){
  if (n.tagName == 'SPAN') return NodeFilter.FILTER_ACCEPT;
  else return NodeFilter.FILTER_SKIP;
 }
 var spans = document.createNodeIterator(
  document,
  NodeFilter.SHOW_ELEMENT,
  spanFilter,
  false
 );
 while((span = spans.nextNode()) != null){
  span.style.color = 'red';
 }
}
setTimeout('load()', 5000);
</script>