var viewportwidth;
var viewportheight;
var objOverlayDiv;
var objOverlayContentDiv ;
var objFrame;
var objTitle;
var contentDivW;
var contentDivH;


function initOverlay(OverLayDivID, ContentDivID, FrameID, TitleID, ContentDivWidth, ContentDivHeight) {
    objOverlayDiv = OverLayDivID;
    objOverlayContentDiv = ContentDivID;
    objFrame = FrameID;
    objTitle = TitleID;
    contentDivW = ContentDivWidth;
    contentDivH = ContentDivHeight;
    window.onresize = function () { rePosition() }
}

function getScreenSize() {

    // mozilla/netscape/opera/IE7
    if (typeof window.innerWidth != 'undefined') {
        viewportwidth = window.innerWidth,
      viewportheight = window.innerHeight
    }
    // IE6 
    else if (typeof document.documentElement != 'undefined'
     && typeof document.documentElement.clientWidth !=
     'undefined' && document.documentElement.clientWidth != 0) {
        viewportwidth = document.documentElement.clientWidth,
       viewportheight = document.documentElement.clientHeight
    }
    // older versions of IE
    else {
        viewportwidth = document.getElementsByTagName('body')[0].clientWidth,
       viewportheight = document.getElementsByTagName('body')[0].clientHeight
    }

}

function rePosition() {
    if (document.getElementById(objOverlayContentDiv).style.display == 'block') {
        getScreenSize();
        document.getElementById(objOverlayContentDiv).style.top = (viewportheight - contentDivW) / 2 + 'px';
        document.getElementById(objOverlayContentDiv).style.left = (viewportwidth - contentDivH) / 2 + 'px';
    }
}

function showOverlay(url, title) {
    getScreenSize();
    document.getElementById(objOverlayDiv).style.display = 'block';

    document.getElementById(objOverlayContentDiv).style.display = 'block';
    document.getElementById(objOverlayContentDiv).style.top = (viewportheight - contentDivW) / 2 + 'px';
    document.getElementById(objOverlayContentDiv).style.left = (viewportwidth - contentDivH) / 2 + 'px';

    document.getElementById(objFrame).src = url;
    document.getElementById(objTitle).innerHTML = title;
}

function closeOverlay() {
    document.getElementById(objFrame).src = '';
    document.getElementById(objOverlayContentDiv).style.display = 'none';
    document.getElementById(objOverlayDiv).style.display = 'none';
}