function tab(x) {
	SetClassUnSelected();
	var id;
	id=x.id.substr(3,1);
	var i=1;
	for (i=1;i<=3;i++)
	{
		if (i==id) {
			document.getElementById("tab"+i).style.display = "block";
		} else {
			document.getElementById("tab"+i).style.display = "none"; 
		}
	}
	SetClassSelected(x);

}

function changeClassSelected(x){
	x.className="selected";
}

function changeClassUnSelected(x){
	x.className="unselected";
}

function SetClassUnSelected(){
	document.getElementById('btn1').className = "unselected";
	document.getElementById('btn2').className = "unselected";
	document.getElementById('btn3').className = "unselected";
}

function SetClassSelected(x){
	x.className = "selected";
}