How to change background Image?

In-completed question, but i guess something.
Actually Image is used as background for DIV. you can change the image by changing the value for background property.
The code is below from the page which you have mentioned.
change the background property value in div.background class in STYLE.

<style type="text/css">
div.background
{
  width: 600px;
  height: 300px;
  background: url('http://www.islamabadid.com/wp-content/uploads/2010/05/Faisal-mosque-Islamabad.jpg') ;
  border: 2px solid black;
}</p>
<p>div.transbox p
{
  margin: 30px 40px;
  font-weight: bold;
  color: #000000;
}
</style>
<p></head><br />
<div class="background">
<div class="transbox">
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</p></div>
</div>
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                </div>
            </div>