Untitled

Align element to bottom of window but allow scrolling to content underneath
var resize = function () {
    var availHeight = window.innerHeight;
    // you need to either calculate
    // or set a fixed offset from the top for content above
    var offset = 80;

    document.getElementById("slider").style.height = availHeight - offset + "px";
}

window.addEventListener("resize", resize, false);
window.addEventListener("load", resize, false);