Why doesn't this piece of code swap images on mouse-over as intended?:

```
<a href="#" onMouseOver="
 if (document.the_image.src == '01.jpg')
 {
  document.the_image.src = '02.jpg';
 }
 else if (document.the_image.src == '02.jpg')
 {
  document.the_image.src = '03.jpg';
 }
 else
 {
  document.the_image.src = '01.jpg';
 }
 ">
Some image</a><br>

```