Get dimensions and position of element

gistfile1.js

function getOffsetRect(elem) {
    var box = elem.getBoundingClientRect(),
        body = document.body,
        docElem = document.documentElement,
        scrollTop = window.pageYOffset || docElem.scrollTop || body.scrollTop,
        scrollLeft = window.pageXOffset || docElem.scrollLeft || body.scrollLeft,
        clientTop = docElem.clientTop || body.clientTop || 0,
        clientLeft = docElem.clientLeft || body.clientLeft || 0,
        top = box.top + scrollTop - clientTop,
        left = box.left + scrollLeft - clientLeft,
        right = box.right + scrollLeft - clientLeft,
        bottom = box.bottom + scrollTop - clientTop;

    return {
        x: Math.round(left),
        y: Math.round(top),
        width: Math.round(right - left),
        height: Math.round(bottom - top)
    };
}​