onload = function() {
    scrollNewsletter( 500 );
}

function scrollNewsletter( x ) {
    document.getElementById( 'newsletterScrollPane' ).style.backgroundPosition =
        ( x = x > -290 ? x - 10 : 500 ) + 'px 0';
    setTimeout( 'scrollNewsletter(' + x + ');', 100 );
}