function changeImage()
		{
			var list = document.getElementById('optionlist');
			document.mainimage.src = list.options[list.selectedIndex].value;
			document.getElementById("caption").innerHTML = list.options[list.selectedIndex].innerHTML;
		}

		function prevImage()
		{
			var list = document.getElementById('optionlist');
			if(list.selectedIndex == 0)
			{
				list.selectedIndex = list.options.length-1;
			}
			else
			{
				list.selectedIndex--;
			}
			changeImage();
		}

		function nextImage()
		{
			var list = document.getElementById('optionlist');
			if(list.selectedIndex == list.options.length-1)
			{
				list.selectedIndex = 0;
			}
			else
			{
				list.selectedIndex++;
			}
			changeImage();
		}