if(document.images) {
  
	var autobiooff =  new Image();
	var autobioon =  new Image();
	var essayoff =  new Image();
	var essayon =  new Image();
	var gameoff =  new Image();
	var gameon =  new Image();
	var polloff =  new Image();
	var pollon =  new Image();
	
	autobiooff.src = "images/sf_book_off.gif";
	autobioon.src = "images/sf_book_on.gif";
	essayoff.src = "images/sf_player_off.gif";
	essayon.src = "images/sf_player_on.gif";
	gameoff.src = "images/sf_streak_off.gif";
	gameon.src = "images/sf_streak_on.gif";
	polloff.src = "images/sf_poll_off.gif";
	pollon.src = "images/sf_poll_on.gif";
}


function off(imgName) {
	if(document.images) {
	document[imgName].src = eval(imgName + 'off.src');
	}
}

function on(imgName) {
	if(document.images) {
	document[imgName].src = eval(imgName + 'on.src');
	}
}