function rollon(_this){
	_this.src = "images/"+_this.id+"_on.jpg";
}

function rolloff(_this){
	_this.src = "images/"+_this.id+"_off.jpg";
}

function rollonpng(_this){
	_this.src = "images/"+_this.id+"_on.png";
}

function rolloffpng(_this){
	_this.src = "images/"+_this.id+"_off.png";
}
function rollongif(_this){
	_this.src = "images/"+_this.id+"_on.gif";
}

function rolloffgif(_this){
	_this.src = "images/"+_this.id+"_off.gif";
}