Javascript Code: Randomly color change

This code changes the background color randomly.
<!-- this script got from www.javascriptfreecode.com coded by: Kerixa Inc. -->
<script>

// Select fade-effect below:
// Set 1 if the background may fade from dark to medium 
// Set 2 if the background may fade from light to medium 
// Set 3 if the background may fade from very dark to very light light
// Set 4 if the background may fade from light to very light
// Set 5 if the background may fade from dark to very dark 
var fade_effect=3

// What type of gradient should be applied Internet Explorer 5x or higher?
// Set "none" or "horizontal" or "vertical"
var gradient_effect="horizontal"

// Speed higher=slower
var speed=60

///////////////////////////////////////////////////////////////////////////
// CONFIGURATION ENDS HERE
///////////////////////////////////////////////////////////////////////////

var browserinfos=navigator.userAgent 
var ie4=document.all&&!document.getElementById
var ie5=document.all&&document.getElementById&&!browserinfos.match(/Opera/)
var ns4=document.layers
var ns6=document.getElementById&&!document.all
var opera=browserinfos.match(/Opera/)  
var browserok=ie4||ie5||ns4||ns6||opera

if (fade_effect==1) {
	var darkmax=1
	var lightmax=127
}
if (fade_effect==2) {
	var darkmax=127
	var lightmax=254
}
if (fade_effect==3) {
	var darkmax=1
	var lightmax=254
}
if (fade_effect==4) {
	var darkmax=190
	var lightmax=254
}
if (fade_effect==5) {
	var darkmax=1
	var lightmax=80
}
var hexc = new Array('0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F')

var newred
var newgreen
var newblue
var oldred
var oldgreen
var oldblue

var redcol_1
var redcol_2 
var greencol_1 
var greencol_2 
var bluecol_1 
var bluecol_2 
var oldcolor
var newcolor
var firsttime=true
 
var stepred=1
var stepgreen=1
var stepblue=1

function setrandomcolor() {
	var range=(lightmax-darkmax)
	if (firsttime) {
		newred=Math.ceil(range*Math.random())+darkmax
		newgreen=Math.ceil(range*Math.random())+darkmax
		newblue=Math.ceil(range*Math.random())+darkmax
		firsttime=false
	}
	
	oldred=Math.ceil(range*Math.random())+darkmax
	oldgreen=Math.ceil(range*Math.random())+darkmax
	oldblue=Math.ceil(range*Math.random())+darkmax
	
	stepred=newred-oldred
	if (oldred>newred) {stepred=1}
	else if (oldred<newred) {stepred=-1}
	else {stepred=0}
	
	stepgreen=newgreen-oldgreen
	if (oldgreen>newgreen) {stepgreen=1}
	else if (oldgreen<newgreen) {stepgreen=-1}
	else {stepgreen=0}
	
	stepblue=newblue-oldblue
	if (oldblue>newblue) {stepblue=1}
	else if (oldblue<newblue) {stepblue=-1}
	else {stepblue=0}
	fadebg()
}

function fadebg() {
	if (newred==oldred) {stepred=0}
	if (newgreen==oldgreen) {stepgreen=0}
	if (newblue==oldblue) {stepblue=0}
	newred+=stepred
	newgreen+=stepgreen
	newblue+=stepblue
	
	if (stepred!=0 || stepgreen!=0 || stepblue!=0) {
      	redcol_1 = hexc[Math.floor(newred/16)];
     	redcol_2 = hexc[newred%16];
	 	greencol_1 = hexc[Math.floor(newgreen/16)];
      	greencol_2 = hexc[newgreen%16];
	  	bluecol_1 = hexc[Math.floor(newblue/16)];
      	bluecol_2 = hexc[newblue%16];
	  	newcolor="#"+redcol_1+redcol_2+greencol_1+greencol_2+bluecol_1+bluecol_2
		if (ie5 && gradient_effect!="none") {
			if (gradient_effect=="horizontal") {gradient_effect=1}
			if (gradient_effect=="vertical") {gradient_effect=0}
      		greencol_1 = hexc[Math.floor(newred/16)];
     		greencol_2 = hexc[newred%16];
	 		bluecol_1 = hexc[Math.floor(newgreen/16)];
      		bluecol_2 = hexc[newgreen%16];
	  		redcol_1 = hexc[Math.floor(newblue/16)];
      		redcol_2 = hexc[newblue%16];
			var newcolorCompl="#"+redcol_1+redcol_2+greencol_1+greencol_2+bluecol_1+bluecol_2
			document.body.style.filter=
"progid:DXImageTransform.Microsoft.Gradient(startColorstr="+newcolorCompl+", endColorstr="+newcolor+" GradientType="+gradient_effect+")"
		}
		else {
	  		document.bgColor=newcolor 
		}
		var timer=setTimeout("fadebg()",speed);
    } 
  	else {
  		clearTimeout(timer)
		newred=oldred
		newgreen=oldgreen
		newblue=oldblue
		oldcolor=newcolor
		setrandomcolor()
  	}
}

if (browserok) {
	window.onload=setrandomcolor
}
</script><a target='_blank' href='http://www.javascriptfreecode.com/' style='font-size: 8pt; text-decoration: none'>JavaScript Codes</a>
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