function getScreenCenterX() {
    return(document.body.clientWidth/2);
}

function getScreenCenterY() {
    var y = 0;
    y = getScrollOffset()+(getInnerHeight()/2);
    return(y);
}

function getScrollOffset() {
    var y;
    if (self.pageYOffset) // all except Explorer
    {
        y = self.pageYOffset;
    } else
        if (document.documentElement && document.documentElement.scrollTop)
        // Explorer 6 Strict
        {
            y = document.documentElement.scrollTop;
        } else
            if (document.body) // all other Explorers
            {
                y = document.body.scrollTop;
            }
    return(y);
}

function getInnerHeight() {
    var y;
    if (self.innerHeight) // all except Explorer
    {
        y = self.innerHeight;
    } else
        if (document.documentElement && document.documentElement.clientHeight)
        // Explorer 6 Strict Mode
        {
            y = document.documentElement.clientHeight;
        } else
            if (document.body) // other Explorers
            {
                y = document.body.clientHeight;
            }
    return(y);
}

function showHideDiv(divName) {
    var elmnt = document.getElementById(divName)
    if (elmnt.style.visibility != "visible") {
        elmnt.style.visibility = "visible";
        elmnt.style.height="150%";
    } else {
        elmnt.style.visibility = "hidden";
        elmnt.style.height="1px";
    }
}

function onOffDiv(divName) {
    var elmnt = document.getElementById(divName)
    if (elmnt.style.visibility != "visible") {
        elmnt.style.visibility = "visible";
    } else {
        elmnt.style.visibility = "hidden";
    }
}