var num = 1;
var Ads = new Array( );

        Ads[0] = ( 'http://www.123.tkcnf.or.jp/ContentsDelivery/Redirector.aspx?key=%3b%2cZ%26%3cXEP%27' );

Rnd = Math.floor( Math.random ( ) * num );
document.write( Ads[Rnd] );