function lightUp(knappid) {
	var knapp = document.getElementById(knappid);
	knapp.style.background = "url('images/" + knappid + "_hover.jpg')";
}

function putOut(knappid) {
	var knapp = document.getElementById(knappid);
	knapp.style.background = "url('images/" + knappid + ".jpg')";
}

function preLoad() {
	
	var antalknappar = 4;
			
	var images = new Array(antalknappar-1);
	var buttons = new Array(antalknappar-1);
	
	buttons[0] = 'start';
	buttons[1] = 'historik';
	buttons[2] = 'aktuellt';
	buttons[3] = 'kontakt';
	
	for(i=0;i<antalknappar-1;i++){
		images[i] = new Image();
		images[i].src = 'images/menu_' + buttons[i] + '_hover.jpg';
	}
	
}