function changebg_pic(site_url,bg_on,picname) {
	var bg1_id=$id('bg_home_malls');
	var bg2_id=$id('bg_shanghai_hq');
	var bg3_id=$id('bg_shanghai_qy');
	var bg4_id=$id('bg_guangzhou');
	var bg5_id=$id('bg_changchun');
	var bg6_id=$id('bg_pazhou');
	for(i=1;i<=6;i++) {
		eval('bg'+i+'_id').style.background="none"; 
	}
	var bg_on_id=$id(bg_on);
	bg_on_id.style.background="url('"+site_url+"images/home_malls_imgbg.jpg')";
	var pic_id=$id('malls_pic');
	pic_id.src=picname;
}