function clickedOutsideElement(elemId, evt) {
    var theElem = '';
    if (window.event)
        theElem = getEventTarget(window.event);
    else theElem = getEventTarget(evt);

    while (theElem != null) {
        if (theElem.id == elemId)
            return false;

        theElem = theElem.offsetParent;
    }

    return true;
}

function getEventTarget(evt) {
    var targ = (evt.target) ? evt.target : evt.srcElement;

    if (targ != null) {
        if (targ.nodeType == 3)
            targ = targ.parentNode;
    }

    return targ;
}

document.onclick = function(evt) {

    var z = GetElement();
    /* if outter element is clicked, close panel */
    if (clickedOutsideElement('SortSlideOutTab', evt) == true) {
        z.style.visibility = 'hidden';
    }
}

function ViewingBtnClick() {
    var z = GetElement();
    if (z.style.visibility == 'visible') {
        z.style.visibility = 'hidden';
    } else {
        z.style.visibility = 'visible'
    }
}

function GetElement() {
    return document.getElementById('MainPanel')
}