var img = new Array();
img[0] = '<img src="./pics/hijiki_after.jpg" alt="ひじき最高だよ" title="ひじき最高">';
img[1] = '<img src="./pics/cats_after.jpg" alt="死にてー" title="自殺願望">';
var randnum = Math.floor(Math.random() * img.length);
document.write(img[randnum]);