function random_pic(pic_place,pic_dir){

var list_length = 4;
pic_num=parseInt(Math.random()*list_length);
pic_num=(isNaN(list_length))?0:pic_num;
document.write(unescape('<img src="'+pic_dir+'headerpic'+ pic_place + pic_num + '.jpg" width="236" height="164" />'));

}