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

//determine the direction for the blending, if start and end are the same nothing happens
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++;
}
}
}

//change the opacity for different browsers
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 blendimage(divid, imageid, imagefile, millisec) {
var speed = Math.round(millisec / 100);
var timer = 0;

//set the current image as background
document.getElementById(divid).style.backgroundImage = "url(" + document.getElementById(imageid).src + ")";

//make image transparent
changeOpac(0, imageid);

//make new image
document.getElementById(imageid).src = imagefile;

//fade in image
for(i = 0; i <= 100; i++) {
setTimeout("changeOpac(" + i + ",'" + imageid + "')",(timer * speed));
timer++;
}
}

function currentOpac(id, opacEnd, millisec) {
//standard opacity is 100
var currentOpac = 100;

//if the element has an opacity set, get it
if(document.getElementById(id).style.opacity < 100) {
currentOpac = document.getElementById(id).style.opacity * 100;
}

//call for the function that changes the opacity
opacity(id, currentOpac, opacEnd, millisec)
}