var img = new Array();
img[0] = '<img src="http://www.kyushu-ec.net/img/catch_01.jpg" alt="九州ECミーティング" width="720" height="200" />';
img[1] = '<img src="http://www.kyushu-ec.net/img/catch_02.jpg" alt="九州ECミーティング" width="720" height="200" />';
img[2] = '<img src="http://www.kyushu-ec.net/img/catch_03.jpg" alt="九州ECミーティング" width="720" height="200" />';
img[3] = '<img src="http://www.kyushu-ec.net/img/catch_04.jpg" alt="九州ECミーティング" width="720" height="200" />';
img[4] = '<img src="http://www.kyushu-ec.net/img/catch_05.jpg" alt="九州ECミーティング" width="720" height="200" />';

var no = Math.floor(Math.random() * img.length);
document.write(img[no]);