nav2_image = new Image();
nav2_image.src = "http://www.sparrowvswallow.com/prototype/frog/images/topnav/header_02.gif";

nav2over_image = new Image();
nav2over_image.src = "http://www.sparrowvswallow.com/prototype/frog/images/topnav/header_2_02.gif";

nav3_image = new Image();
nav3_image.src = "http://www.sparrowvswallow.com/prototype/frog/images/topnav/header_03.gif";

nav3over_image = new Image();
nav3over_image.src = "http://www.sparrowvswallow.com/prototype/frog/images/topnav/header_2_03.gif";


nav4_image = new Image();
nav4_image.src = "http://www.sparrowvswallow.com/prototype/frog/images/topnav/header_04.gif";

nav4over_image = new Image();
nav4over_image.src = "http://www.sparrowvswallow.com/prototype/frog/images/topnav/header_2_04.gif";

nav5_image = new Image();
nav5_image.src = "http://www.sparrowvswallow.com/prototype/frog/images/topnav/header_05.gif";

nav5over_image = new Image();
nav5over_image.src = "http://www.sparrowvswallow.com/prototype/frog/images/topnav/header_2_05.gif";


nav6_image = new Image();
nav6_image.src = "http://www.sparrowvswallow.com/prototype/frog/images/topnav/header_06.gif";

nav6over_image = new Image();
nav6over_image.src = "http://www.sparrowvswallow.com/prototype/frog/images/topnav/header_2_06.gif";


nav7_image = new Image();
nav7_image.src = "http://www.sparrowvswallow.com/prototype/frog/images/topnav/header_07.gif";

nav7over_image = new Image();
nav7over_image.src = "http://www.sparrowvswallow.com/prototype/frog/images/topnav/header_2_07.gif";




<!-- repeat the 4 lines above for any subsequent images. -->

function swap(){
if (document.images){
for (var x=0;
x<swap.arguments.length;
x+=2) {
document[swap.arguments[x]].src = eval(swap.arguments[x+1] + ".src");
}
}
}