var block4="<table width='724' border='0' cellspacing='0' cellpadding='0' class='index_img'><tr><td rowspan='3' class='right_2'><a href='http://www.google.co.jp' target='_self'><img src='images/428_238.jpg' width='482' height='238' border='0' /></a></td><td class='left_2 bottom_2'><img src='images/238_76.jpg' width='238' height='76'  border='0'/></td></tr><tr><td class='top_3 left_2 bottom_3'><img src='images/238_76_3.jpg' width='238' height='76'  border='0'/></td></tr><tr><td class='top_2 left_2'><a href='http://www.google.co.jp' target='_self'><img src='images/238_76_2.jpg' width='238' height='76'  border='0'/></a></td></tr></table>";

var block4_2="<table width='724' border='0' cellspacing='0' cellpadding='0' class='index_img'><tr><td rowspan='3' class='right_2'><a href='http://www.google.co.jp' target='_self'><img src='images/428_238_2.jpg' width='482' height='238' border='0' /></a></td><td class='left_2 bottom_2'><img src='images/238_76.jpg' width='238' height='76'  border='0'/></td></tr><tr><td class='top_3 left_2 bottom_3'><a href='http://www.google.co.jp' target='_self'><img src='images/238_76_2.jpg' width='238' height='76'  border='0'/></a></td></tr><tr><td class='left_2 top_2'><a href='http://www.google.co.jp' target='_self'><img src='images/238_76_3.jpg' width='238' height='76'  border='0'/></a></td></tr></table>";

var block7="<table width='724' border='0' cellspacing='0' cellpadding='0' class='index_img'><tr><td colspan='2' rowspan='2' class='right_2 bottom_3'><a href='http://www.google.co.jp' target='_self'><img src='images/428_158.jpg' width='482' height='157' border='0' /></a></td><td class='left_2 bottom_2'><a href='http://www.google.co.jp' target='_self'><img src='images/238_76_2.jpg' width='238' height='76'  border='0'/></a></td></tr><tr><td class='left_2 bottom_3 top_3'><a href='http://www.google.co.jp' target='_self'><img src='images/238_76.jpg' width='238' height='76'  border='0'/></a></td></tr><tr><td class='top_2 right_3'><a href='http://www.google.co.jp' target='_self'><img src='images/238_76.jpg' width='238' height='76'  border='0'/></a></td><td class='top_2 left_3 right_2'><a href='http://www.google.co.jp' target='_self'><img src='images/238_76_3.jpg' width='238' height='76'  border='0'/></a></td><td class='top_2 left_2'><a href='http://www.google.co.jp' target='_self'><img src='images/238_76.jpg' width='238' height='76'  border='0'/></a></td></tr></table>";

var topimg = [block4,block4_2,block7];
var ran = topimg.length;
var topimg = topimg[Math.floor(Math.random()*ran)];