var billboardFadeSpeed = 4000;
var billboardPause = 7000;

$(document).ready(function(){startBillboards();});

function startBillboards()
{
   $("#billboards").append("<input type='hidden' id='currentBillboard' value='0' />");
   showNextBillboard();
}

function hideBillboard()
{
   var billboardString = "#billboard"+$("#currentBillboard").val();
   $(billboardString).fadeOut(billboardFadeSpeed);
showNextBillboard();
}

function showNextBillboard()
{
    var nextIndex = +$("#currentBillboard").val() + 1;

    // Check that next billboard exists else reset to 1
    //
    if(!$("#billboard"+nextIndex).length)
    {
        nextIndex= 1;
    }

    $("#billboard"+nextIndex).fadeIn(billboardFadeSpeed);
    $("#currentBillboard").val(nextIndex);

    window.setTimeout(hideBillboard, billboardPause);
}