var c=0
var s

function mainbanner()
{
if (c%5==0){
document.getElementById('thegrassdoctor').src = "ban_thegrassdoctor1.jpg";
}
if (c%5==1){
document.getElementById('thegrassdoctor').src = "ban_thegrassdoctor1.jpg";
}
if (c%5==2){
document.getElementById('thegrassdoctor').src = "ban_thegrassdoctor2.jpg";
}
if (c%5==3){
document.getElementById('thegrassdoctor').src = "ban_thegrassdoctor3.jpg";
}
if (c%5==4){
document.getElementById('thegrassdoctor').src = "ban_thegrassdoctor4.jpg";
}
c=c+1
s=setTimeout("mainbanner()",4000)   //<time in milliseconds
}