var currentDiv = 0;
var nextDiv = 0;
function HeaderRefresh() {
    HiddeHeaderPictures();
    GetHeaderNextPicture();
    DisplayHeaderPictures();
}
function HiddeHeaderPictures() {
    for (var i = 1; i <= headerCount; i++) {                   
        document.getElementById('header_' + i).style.display = 'none';
    }
}

function GetHeaderNextPicture() {
    if (currentDiv < headerCount) {
        if (currentDiv >= 0) {
            nextDiv = currentDiv + 1;
        }
    } else {
    nextDiv++;
    }
}

function DisplayHeaderPictures() {
    for (var i = 1; i <= headerCount; i++) {
        if (i == nextDiv) {
            document.getElementById('header_' + i).style.display = 'block';
            currentDiv = i;
            nextDiv = 0;
        }
    }
}
HeaderRefresh();
setInterval('HeaderRefresh()', intervalSeconds * 1000);