var screenIndex = 1;

function initScreens() {
    setTimeout("switchScreens()", 5000);
}

function switchScreens() {
    var screenIndexPre = screenIndex;

    if (screenIndex == 5) {
        screenIndex = 1;
    } else {
        screenIndex++;
    }

    new Effect.Appear("screen" + screenIndex, { duration:0.5 });
    new Effect.Fade("screen" + screenIndexPre, { duration:0.5 });

    setTimeout("switchScreens()", 5000);
}