function getOffset(elem) {
    if (elem.getBoundingClientRect) {
        // "правильный" вариант
        return getOffsetRect(elem)
    } else {
        // пусть работает хоть как-то
        return getOffsetSum(elem)
    }
}

function getOffsetSum(elem) {
    var top=0, left=0
    while(elem) {
        top = top + parseInt(elem.offsetTop)
        left = left + parseInt(elem.offsetLeft)
        elem = elem.offsetParent
    }

    return {top: top, left: left}
}

function getOffsetRect(elem) {
    // (1)
    var box = elem.getBoundingClientRect()

    // (2)
    var body = document.body
    var docElem = document.documentElement

    // (3)
    var scrollTop = window.pageYOffset || docElem.scrollTop || body.scrollTop
    var scrollLeft = window.pageXOffset || docElem.scrollLeft || body.scrollLeft

    // (4)
    var clientTop = docElem.clientTop || body.clientTop || 0
    var clientLeft = docElem.clientLeft || body.clientLeft || 0

    // (5)
    var top  = box.top +  scrollTop - clientTop
    var left = box.left + scrollLeft - clientLeft

    return { top: Math.round(top), left: Math.round(left) }
}

function getClientHeight() {
	return document.compatMode=='CSS1Compat' && !window.opera?document.documentElement.clientHeight:document.body.clientHeight;
}

function getClientWidth() {
	return document.compatMode=='CSS1Compat' && !window.opera?document.documentElement.clientWidth:document.body.clientWidth;
}

var ua = navigator.userAgent.toLowerCase();
var isOpera = (ua.indexOf('opera')  > -1);
var isIE = (!isOpera && ua.indexOf('msie') > -1);

function getDocumentHeight() {
  return Math.max(document.compatMode != 'CSS1Compat' ? document.body.scrollHeight : document.documentElement.scrollHeight, getViewportHeight());
}

function getDocumentWidth() {
  return Math.max(document.compatMode != 'CSS1Compat' ? document.body.scrollWidth : document.documentElement.scrollWidth, getViewportWidth());
}

function getViewportHeight() {
  return ((document.compatMode || isIE) && !isOpera) ? (document.compatMode == 'CSS1Compat') ? document.documentElement.clientHeight : document.body.clientHeight : (document.parentWindow || document.defaultView).innerHeight;
}

function getViewportWidth() {
  return ((document.compatMode || isIE) && !isOpera) ? (document.compatMode == 'CSS1Compat') ? document.documentElement.clientWidth : document.body.clientWidth : (document.parentWindow || document.defaultView).innerWidth;
}