var how_many_ads = 4;
var now = new Date()
var sec = now.getSeconds()
var ad = sec % how_many_ads;
ad +=1;

<!--  -----------------------  -->
<!--    Home Graphic 1 of 7    -->
<!--  -----------------------  -->

if (ad==1) {
txt=".";
url="#"; 
alt=".";
banner="/images/photo10.jpg"; 
width="300"; 
height="200";
}

<!--  -----------------------  -->
<!--    Home Graphic 2 of 7    -->
<!--  -----------------------  -->

if (ad==2) {
txt=".";
url="#"; 
alt=".";
banner="/images/photo12.jpg"; 
width="300"; 
height="200";
}

<!--  -----------------------  -->
<!--    Home Graphic 3 of 7    -->
<!--  -----------------------  -->

if (ad==3) {
txt=".";
url="#"; 
alt=".";
banner="/images/photo13.jpg"; 
width="300"; 
height="200";
}

<!--  -----------------------  -->
<!--    Home Graphic 4 of 7    -->
<!--  -----------------------  -->

if (ad==4) {
txt=".";
url="#"; 
alt=".";
banner="/images/photo14.jpg"; 
width="300"; 
height="200";
}

<!--  -----------------------  -->
<!--    Home Graphic 5 of 7    -->
<!--  -----------------------  -->

if (ad==5) {
txt=".";
url="#"; 
alt=".";
banner="/images/photo19.jpg"; 
width="300"; 
height="200";
}

<!--  -----------------------  -->
<!--    Home Graphic 6 of 7    -->
<!--  -----------------------  -->

if (ad==6) {
txt=".";
url="#"; 
alt=".";
banner="/images/photo20.jpg"; 
width="300"; 
height="200";
}

<!--  -----------------------  -->
<!--    Home Graphic 7 of 7    -->
<!--  -----------------------  -->

if (ad==7) {
txt=".";
url="#"; 
alt=".";
banner="/images/photo21.jpg"; 
width="300"; 
height="200";
}

document.write('<center>');
document.write('<img src=\"' + banner + '\" width=')
document.write(width + ' height=' + height + ' ');
document.write('alt=\"' + alt + '\" border=0><br>');
document.write('</center>');