function opacity(id, opacStart, opacEnd, millisec) {
    //geschwindigkeit (dauer pro frame)
    var speed = Math.round(millisec / 100);
    var timer = 0;

    //ein- oder ausblenden?
    if(opacStart > opacEnd) {
        for(i = opacStart; i >= opacEnd; i--) {
            setTimeout("changeOpac(" + i + ",'" + id + "')",(timer * speed));
            timer++;
        }
    } else if(opacStart < opacEnd) {
        for(i = opacStart; i <= opacEnd; i++)
            {
            setTimeout("changeOpac(" + i + ",'" + id + "')",(timer * speed));
            timer++;
        }
    }
}

//opacity ändern für die verschiedenen browser
function changeOpac(opacity, id) {
    var object = document.getElementById(id).style;
    object.opacity = (opacity / 100);
    object.MozOpacity = (opacity / 100);
    object.KhtmlOpacity = (opacity / 100);
    object.filter = "alpha(opacity=" + opacity + ")";
}

function shiftOpacity(id, millisec) {
    //if an element is invisible, make it visible, else make it ivisible
    if(document.getElementById(id).style.opacity == 0) {
        opacity(id, 0, 100, millisec);
    } else {
        opacity(id, 100, 0, millisec);
    }
} 

function fadeIn(id, millisec)
{
	if(document.getElementById(id).style.opacity < 100)
		opacity(id, 0, 100, millisec);
}

function fadeOut(id, millisec)
{
	if(document.getElementById(id).style.opacity > 0)
		opacity(id, 100, 0, millisec);
}