window.onload = rotate; 

var Pics = new 
Array("http://www.triuhistory.ca/images/header1.jpg","http://www.triuhistory.ca/images/header2.jpg","http://www.triuhistory.ca/images/header3.jpg","http://www.triuhistory.ca/images/header4.jpg","http://www.triuhistory.ca/images/header5.jpg");
var thisPic = 0;

function rotate() {
thisPic++;
if (thisPic == Pics.length){
thisPic = 0;
}
document.getElementById("slideshow").src = Pics[thisPic];
setTimeout("rotate()", 3*1500);
}