[Costin Trifan]

you need to change the target, so your function would become:

function changeImage(filename, target)
{
document.target.src = filename;
}

and in your file:

      <p align="center"> <img name="mainimage"
 src="DSCF2715.JPG"></p>
      <p align="center">Images: <a
 href="javascript:changeImage('DSCF2715.JPG', 'mainimage')">1</a>
      <a href="javascript:changeImage('DSCF0605.JPG', 'mainimage')">2</a>
      <a href="javascript:changeImage('image3.jpg', 'mainimage')">3</a>
      <a href="javascript:changeImage('image4.jpg', 'mainimage')">4</a>
      <a href="javascript:changeImage('image5.jpg', 'mainimage')">5</a></p>



      <p align="center"> <img name="mainimage2"
 src="DSCF2715.JPG"></p>
      <p align="center">Images: <a
 href="javascript:changeImage('DSCF2715.JPG', 'mainimage2')">1</a>
      <a href="javascript:changeImage('DSCF0605.JPG', 'mainimage2')">2</a>
      <a href="javascript:changeImage('image3.jpg', 'mainimage2')">3</a>
      <a href="javascript:changeImage('image4.jpg', 'mainimage2')">4</a>
      <a href="javascript:changeImage('image5.jpg', 'mainimage2')">5</a></p>

I think this should do it