window.onload = choosePic;

	var myPix = new 
Array("images/header_slide1.jpg", "images/header_slide2.jpg", "images/header_slide3.jpg","images/header_slide4.jpg", "images/header_slide5.jpg", "images/header_slide6.jpg", "images/header_slide7.jpg", "images/header_slide8.jpg", "images/header_slide9.jpg", "images/header_slide10.jpg", "images/header_slide11.jpg", "images/header_slide12.jpg");
  
	function choosePic() {
		randomNum = Math.floor((Math.random() * myPix.length));
		document.getElementById("myPicture").src = myPix[randomNum];
	}