I select some text on the html page(opened in firefox) using mouse,and using javascript functions, i create/get the rangeobject corresponding to the selected text.

 userSelection =window.getSelection(); 
 var rangeObject = getRangeObject(userSelection);

Now i want to highlight all the text which comes under the rangeobject.I am doing it like this,

  var span = document.createElement("span");
  rangeObject.surroundContents(span);
  span.style.backgroundColor = "yellow";

Well,this works fine, only when the rangeobject(startpoint and endpoint) lies in the same textnode,then it highlights the corresponding text.Ex

    <p>In this case,the text selected will be highlighted properly,
       because the selected text lies under a single textnode</p>

But if the rangeobject covers more than one textnode, then it is not working properlay, It highlights only the texts which lie in the first textnode,Ex

 <p><h3>In this case</h3>, only the text inside the header(h3) 
  will be highlighted, not any text outside the header</p> 

Any idea how can i make, all the texts which comes under rangeobject,highlighted,independent of whether range lies in a single node or multiple node? Thanks....