function random_imglink(){

  var myimages=new Array()
  myimages[1]="/images/banners/bhouse_ad.gif"
  myimages[2]="/images/banners/stnetwork_ad.gif"
  myimages[3]="/images/banners/nativeplants_ad.gif"
  myimages[4]="/images/banners/enviroweather_ad.gif"

  var imagelinks=new Array()
  imagelinks[1]="http://www.bughouse.msu.edu"
  imagelinks[2]="http://www.stewardshipnetwork.org"
  imagelinks[3]="http://nativeplants.msu.edu"
  imagelinks[4]="http://www.enviroweather.msu.edu"

  var ry=Math.floor(Math.random()*myimages.length)

  if (ry==0)
     ry=1
     document.write('<a href='+'"'+imagelinks[ry]+'"'+'><img src="'+myimages[ry]+'" border=0></a>')
}

 random_imglink()