function $(id) {
    return document.getElementById(id);
}
var useOpacity =
    (typeof document.createElement("div").style.opacity != 'undefined');
var useFilter = !useOpacity
    && (typeof document.createElement("div").style.filter != 'undefined');

function setOpacity(el, value) {
    // let el be either an element object or an id string
    if (typeof el == 'string')
        el = document.getElementById(el);

    // ensure value is in [0-1] range
    value = Math.min(1, Math.max(value, 0));

    // set opacity or filter alpha depending on what's supported
    if (useOpacity)
        el.style.opacity = value;
    else if (useFilter)
        el.style.filter = "alpha(opacity=" + (value * 100) + ")";
}
function returnOpacity(el) {
    // let el be either an element object or an id string
    if (typeof el == 'string')
        el = document.getElementById(el);

    // set opacity or filter alpha depending on what's supported
    if (useOpacity)
        return 1*el.style.opacity;
    else if (useFilter)
        return 1*(el.style.filter.replace(/[^0-9]+/gi, '')/100);
}