var zIndice=1000;
var current=0;
var play=1;
var ssSpeed=6000;

var t=setInterval("nextSlide()",ssSpeed);

function updateBut(){
	var tmp = current + 1;
	if(play==1)
		document.getElementById("pp_but").src="images/but_pause.gif";	
	else
		document.getElementById("pp_but").src="images/but_play.gif";
}

function butReset(){
	document.getElementById("slide1_but").src="images/but_1.gif";
	document.getElementById("slide2_but").src="images/but_2.gif";
	document.getElementById("slide3_but").src="images/but_3.gif";
	document.getElementById("slide4_but").src="images/but_4.gif";	
}

function opacity(id) {
	if(play==1) clearInterval(t);
	if(document.getElementById(id).style.zIndex!=zIndice){
		var millisec = 700;
		var speed = Math.round(millisec / 100);
		var timer = 0;
		changeOpac(0,id,0);
		zIndice++;
		butReset();
			if(id=="slide1"){
				current=0;
				document.getElementById("slide1_but").src="images/but_1_sel.gif";
			} else if(id=="slide2"){
				current=1;
				document.getElementById("slide2_but").src="images/but_2_sel.gif";
			} else if(id=="slide3"){
				current=2;
				document.getElementById("slide3_but").src="images/but_3_sel.gif";
			} else {
				current=3;
				document.getElementById("slide4_but").src="images/but_4_sel.gif";
			}
			
		document.getElementById(id).style.zIndex=zIndice;
		for(i = 0; i <= 100; i++)
			{
				setTimeout("changeOpac(" + i + ",'" + id + "')",(timer * speed));
				timer++;
			}
	}
	if(play==1) t=setInterval("nextSlide()",ssSpeed);
}

function pp(){
	
	if(play==1)
		clearInterval(t);
	else
		t=setInterval("nextSlide()",ssSpeed);
		
	play = (play+1)%2
	updateBut();
}

function nextSlide(){
	current = (current+1)%4;
	var tmpStr = "slide" + (current+1);
	opacity(tmpStr);
}

function prevSlide(){
	current = (current+3)%4;
	var tmpStr = "slide" + (current+1);
	opacity(tmpStr);
}

//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 + ")";
}