var txt = new Array();
txt[0]="<a href='http://www.123-navi.com/one-flow/'><img src='http://www.123-navi.com/bana/019_one-flow.jpg'  width='100%' border=0></a>";
txt[1]="<a href='http://www.123-navi.com/sawasdee/'><img src='http://www.123-navi.com/bana/023_sawasdee.gif'  width='100%' border=0></a>";
txt[2]="<a href='http://www.123-navi.com/fujichu/'><img src='http://www.123-navi.com/bana/017_fujichu.gif'  width='100%' border=0></a>";
txt[3]="<a href='http://www.123-navi.com/fukusuke/'><img src='http://www.123-navi.com/bana/013_fukusuke.gif'  width='100%' border=0></a>";
txt[4]="<a href='http://www.123-navi.com/metamorpose/'><img src='http://www.123-navi.com/bana/014_meta.gif'  width='100%' border=0></a>";

mmax = 5; //メッセージ行数
txtno = Math.floor(Math.random() * mmax);
document.write(txt[txtno]);