var imageArray = new Array();

imageArray[0] = "../grfx/photography/headers/Banner_1.jpg"; 
imageArray[1] = "../grfx/photography/headers/Banner_2.jpg";
imageArray[2] = "../grfx/photography/headers/Banner_3.jpg";
imageArray[3] = "../grfx/photography/headers/Banner_4.jpg";
imageArray[4] = "../grfx/photography/headers/Banner_5.jpg";
function doIt()
{
var rand = Math.floor(Math.random()*5);

var imgPath = "<img src='"+imageArray[rand]+"' alt='header' border='0' />";

document.getElementById("header").innerHTML = imgPath;

}