window.onload = choosePic;

var myPix = new Array("_images-site/site-sign-delivery.png","_images-site/site-sign-offers.png","_images-site/site-sign-visit.png");

function choosePic() {
	randomNum = Math.floor((Math.random() * myPix.length));
	document.getElementById("randomSign").src = myPix[randomNum];
}