var prevPic = "pic1";
function show(image) {
	var lastPic = document.getElementById(prevPic);
	var mainPic = document.getElementById(image);
	var background = document.getElementById('centreText');
	lastPic.style.display = 'none';
	mainPic.style.display = 'inline';
	mainPic.style.zIndex = 10;
	prevPic = image;
	background.style.opacity = .5;
	background.style.MozOpacity = .5;
    background.style.KhtmlOpacity = .5;
    background.style.filter = "alpha(opacity= '50')";
}
function hide(image) {
	var mainPic = document.getElementById(image);
	var background = document.getElementById('centreText');
	mainPic.style.display = 'none';
	background.style.opacity = 1;
    background.style.MozOpacity = 1;
    background.style.KhtmlOpacity = 1;
    background.style.filter = "alpha(opacity= '100')";
}