function topBg() {
	bgc = new Array();
	bgc[0] = "url(/_img/topbg/01.jpg)";
	bgc[1] = "url(/_img/topbg/02.jpg)";
	bgc[2] = "url(/_img/topbg/03.jpg)";
	bgc[3] = "url(/_img/topbg/04.jpg)";
	bgc[4] = "url(/_img/topbg/05.jpg)";
	bgc[5] = "url(/_img/topbg/06.jpg)";
	bgc[6] = "url(/_img/topbg/07.jpg)";
	bgc[7] = "url(/_img/topbg/08.jpg)";
	bgc[8] = "url(/_img/topbg/09.jpg)";
	bgc[9] = "url(/_img/topbg/10.jpg)";
	bgc[10] = "url(/_img/topbg/11.jpg)";
	bgc[11] = "url(/_img/topbg/12.jpg)";
	n = Math.floor(Math.random()*bgc.length);
	document.getElementById("header").style.backgroundImage = bgc[n]
}