function randomImage(){
			//picks a random number
			var seed, rnum, rand;
			var altText = "Langtons Chartered Accountants and Business Advisers";//change to alter alt text in image tag
			var idType ="headerImg"
			imageNum = 4;//number of images you have
			rnum = index = Math.round(Math.random() * (imageNum -1))
			
			//puts image names into an array
			var theimage = new Array();
			theimage[0] = "/images/picture_01.jpg";
			theimage[1] = "/images/picture_02.jpg";
			theimage[2] = "/images/picture_03.jpg";
			theimage[3] = "/images/picture_04.jpg";
			
			//writes the line to display the random image
			document.write('<img src=\"' + theimage[rnum] + '\" id=\"' + idType + '\"  hspace=\"0\" vspace=\"0\" border=\"0\" alt=\"' + altText + '\ /">');
/*to use in a page link to this file in the header and put this code where you want the image to appear: <script type="text/javascript">
randomImage();</script> You can also put a <noscript> after it for a static image.*/
}