Here I modify your code. Please check if it works well :
<img src="images/i1.jpg" id="slide" height="200" width="500px" alt="" name="slide" />
<script type="text/javascript">
var slideimages = new Array()
slideimages[0] = new Image()
slideimages[0].src = "images/i1.jpg"
slideimages[1] = new Image()
slideimages[1].src = "images/i2.jpg"
slideimages[2] = new Image()
slideimages[2].src = "images/i3.jpg"
var pauseSlide = true;
var step = 0
function slideit() {
document.getElementById("slide").onmouseover = function () {
pauseSlide = false;
};
document.getElementById("slide").onmouseout = function () {
pauseSlide = true;
};
if (!document.images)
return
if (pauseSlide) {
document.getElementById('slide').src = slideimages[step].src
if (step < 2)
step++
else
step = 0
}
setTimeout("slideit()", 500);
}
slideit();
</script>
Hope it helps you.
Good luck.