fadeSpeed = 15


function setOpacity(layerName,value,fadeStep) {
	document.getElementById(layerName).style.opacity = value/fadeStep;
	document.getElementById(layerName).style.filter = 'alpha(opacity=' + value*100/fadeStep + ')';
	}

function fading_on(){
	clearTimeout(this.timer)
	this.setOpacity(this.layerName,this.i,this.fadeStep)
	this.i++
	if (this.i <= this.fadeStep){this.timer = eval('setTimeout("'+this.fadingObj+'.fading_on()",fadeSpeed)');}
	else if (this.expr1!=""){this.timer=eval(this.expr1);}
	}

function fading_off(){
	clearTimeout(this.timer)
	this.setOpacity(this.layerName,this.i,this.fadeStep)
	this.i--
	if (this.i >= 0){this.timer = eval('setTimeout("'+this.fadingObj+'.fading_off()",fadeSpeed)');}
	else if (this.expr2!=""){this.timer=eval(this.expr2);}
	}

function fading_obj(fadingObj,layerName,fadeStep,expr1,expr2){
	this.fadingObj = fadingObj;	
	this.layerName = layerName;	
	this.fadeStep = fadeStep;
	this.expr1 = expr1
	this.expr2 = expr2
	this.i = 0
	this.timer = 0
	this.fading_on = fading_on;
	this.fading_off = fading_off;
	this.setOpacity = setOpacity;
	}