function changeBox1(){
document.getElementById("box1_main").style.backgroundImage = "url('top_l.jpg')";
document.getElementById("box1_cap").style.backgroundImage = "url('top_r.jpg')";

	document.getElementById("box2_main").style.backgroundImage = "url('btm_l.jpg')";
	document.getElementById("box2_cap").style.backgroundImage = "url('btm_r.jpg')";
	
	document.getElementById("box3_main").style.backgroundImage = "url('btm_l.jpg')";
	document.getElementById("box3_cap").style.backgroundImage = "url('btm_r.jpg')";
	
	document.getElementById("box4_main").style.backgroundImage = "url('btm_l.jpg')";
	document.getElementById("box4_cap").style.backgroundImage = "url('btm_r.jpg')";	
}

function changeBox2(){
document.getElementById("box2_main").style.backgroundImage = "url('top_l.jpg')";
document.getElementById("box2_cap").style.backgroundImage = "url('top_r.jpg')";

	document.getElementById("box1_main").style.backgroundImage = "url('btm_l.jpg')";
	document.getElementById("box1_cap").style.backgroundImage = "url('btm_r.jpg')";
	
	document.getElementById("box3_main").style.backgroundImage = "url('btm_l.jpg')";
	document.getElementById("box3_cap").style.backgroundImage = "url('btm_r.jpg')";
	
	document.getElementById("box4_main").style.backgroundImage = "url('btm_l.jpg')";
	document.getElementById("box4_cap").style.backgroundImage = "url('btm_r.jpg')";
}

function changeBox3(){
document.getElementById("box3_main").style.backgroundImage = "url('top_l.jpg')";
document.getElementById("box3_cap").style.backgroundImage = "url('top_r.jpg')";

	document.getElementById("box1_main").style.backgroundImage = "url('btm_l.jpg')";
	document.getElementById("box1_cap").style.backgroundImage = "url('btm_r.jpg')";
	
	document.getElementById("box2_main").style.backgroundImage = "url('btm_l.jpg')";
	document.getElementById("box2_cap").style.backgroundImage = "url('btm_r.jpg')";
	
	document.getElementById("box4_main").style.backgroundImage = "url('btm_l.jpg')";
	document.getElementById("box4_cap").style.backgroundImage = "url('btm_r.jpg')";

}

function changeBox4(){
document.getElementById("box4_main").style.backgroundImage = "url('top_l.jpg')";
document.getElementById("box4_cap").style.backgroundImage = "url('top_r.jpg')";

	document.getElementById("box1_main").style.backgroundImage = "url('btm_l.jpg')";
	document.getElementById("box1_cap").style.backgroundImage = "url('btm_r.jpg')";
	
	document.getElementById("box2_main").style.backgroundImage = "url('btm_l.jpg')";
	document.getElementById("box2_cap").style.backgroundImage = "url('btm_r.jpg')";
	
	document.getElementById("box3_main").style.backgroundImage = "url('btm_l.jpg')";
	document.getElementById("box3_cap").style.backgroundImage = "url('btm_r.jpg')";	
}