var onder = 1
var boven = 40

var jpg = Math.floor(Math.random() * (boven-onder)) + onder

// if ( /okavango/.test(location.href) || /data_botswana/.test(location.href) ) { jpg = 'meander';  }

document.write('<img name="index" src="images/head.jpg" width="700" height="79" border="0" usemap="#m_index" alt="">')

document.write('<br><img src="images/heads/'+jpg+'.jpg" border="0" height="154" width="700"><br>')