function random_number(n) {
	var x;
	x=Math.round(Math.random()*100);
	x%=n;
	return x;
}

function banner() {
	var img = new Array();
	img[0]='<a href="#" target="_blank"><img src="../headers/var_1.jpg" border=0 width=594 height=90 alt=""></a>';
	img[1]='<a href="#" target="_blank"><img src="../headers/var_2.jpg" border=0 width=594 height=90 alt=""></a>';
	img[2]='<a href="#" target="_blank"><img src="../headers/var_3.jpg" border=0 width=594 height=90 alt=""></a>';
	img[3]='<a href="#" target="_blank"><img src="../headers/var_4.jpg" border=0 width=594 height=90 alt=""></a>';

	var n=random_number(4); 
	document.write(img[n]);
}