function setContentPic() {
	var url = document.URL;
	var htmlfile = url.lastIndexOf("\.html"); // -1 = root directory with no .html file extension ie we are in index.html
	var indexfile = url.lastIndexOf("index\.html"); // -1 = we are not in index.html
	var rand_no = Math.ceil(12*Math.random());
	document.getElementById('content-pic').style.backgroundImage='url(images/gallery/'+rand_no+'.jpg)';
	if ((indexfile != -1) || (htmlfile == -1)) // ie we are either in index.html or in the root with no .html which therefore equals index.html
	{
	document.getElementById('content-pic').style.display='none';
	document.getElementById('content').style.display='none';
	}
}