function changeColour(elementId) {
	var interval = 500;
	var colour1 = "#ff0000", colour2 = "black";
	if (document.getElementById) {
		var element = document.getElementById(elementId);
		element.style.color = (element.style.color == colour1) ? colour2 : colour1;
		setTimeout("changeColour('" + elementId + "')", interval);
	}
}