var image1=new Image (); image1.src="images/slide_1.png";
var image2=new Image (); image2.src="images/slide_2.png";
var image3=new Image (); image3.src="images/slide_3.png";
var image4=new Image (); image4.src="images/slide_4.png";

var step=1

function slideshow(){
//if browser does not support the image object, exit.
if (!document.images)
return
document.images.slide.src=eval("image"+step+".src")
if (step<4)
step++
else
step=1
//call function "slideshow()" every 2.5 seconds
setTimeout("slideshow()",5000)
}
slideshow()