//random header
var header_count = 6;//change according to number of headers available, header1.png, header2.png, and so on
var random_pu = parseInt(Math.random()*header_count) + 1;
var random_header = 'slide' + random_pu + '.jpg';
document.getElementById('brand').style.backgroundImage = 'url("/phpBB2/styles/alltrac/template/css/headers/'+random_header+'")';