var txt = new Array();
txt[0]="../../images/exp/ico000.gif";
txt[1]="../../images/exp/ico001.gif";
txt[2]="../../images/exp/ico002.gif";
txt[3]="../../images/exp/ico003.gif";
txt[4]="../../images/exp/ico004.gif";
txt[5]="../../images/exp/ico005.gif";

mmax = 5; //メッセージ行数
txtno = Math.floor(Math.random() * mmax);
document.write("<img src='"+txt[txtno]+"'>");