var c = 0;
    function changeColor()
    {
        if ( c++ % 2 )
        {
        document.getElementById('ad').style.backgroundColor = 'red';
        }
        else
        {
        document.getElementById('ad').style.backgroundColor = '#AA0000';
        }

        setTimeout ( "changeColor()", 1000 );
    }

    window.onload = function() { setTimeout ( "changeColor()", 1000 ); }