var max=4;
var thisBanner=1;
var banner=new MakeBannerArray(max);

function MakeBannerArray(n)
{
this.length=n;
for (var i=1; i<=n;i++)
{
this[i]="";
}
return this;
} 

banner[1]='<img src="http://www.airportnetwork.com/_source/images/random01.jpg" width="920" height="178"><\/a>';
banner[2]='<img src="http://www.airportnetwork.com/_source/images/random02.jpg" width="920" height="178"><\/a>';
banner[3]='<img src="http://www.airportnetwork.com/_source/images/random03.jpg" width="920" height="178"><\/a>';
banner[4]='<img src="http://www.airportnetwork.com/_source/images/random04.jpg" width="920" height="178"><\/a>';

function rand(n)
      {
      rnum=Math.floor(n*Math.random())+1;
      return rnum;
      } 

function setBanner()
      {
      thisBanner=rand(max);
      }