window.onload = choosePic;

var adImages = new Array("images/slide1.jpg","images/slide2.jpg","images/slide3.jpg","images/slide4.jpg","images/slide5.jpg","images/slide6.jpg","images/slide7.jpg","images/slide8.jpg","images/slide9.jpg","images/slide10.jpg","images/slide11.jpg","images/slide12.jpg");
var thisAd = 0;

function choosePic() {
	thisAd = Math.floor((Math.random() * adImages.length));
	document.getElementById("slideshow").src = adImages[thisAd];
	
	rotate();
}

function rotate() {
	thisAd++;
	if (thisAd == adImages.length) {
		thisAd = 0;
	}
	document.getElementById("slideshow").src = adImages[thisAd];

	setTimeout(rotate, 4 * 1000);
}