function getHeight() {
    var height = 0;

    if (window.innerHeight)
    {
        height = window.innerHeight - 18;
    }
    else if ((document.documentElement) && (document.documentElement.clientHeight))
    {
        height = document.documentElement.clientHeight;
    }
    else if ((document.body) && (document.body.clientHeight))
    {
        height = document.body.clientHeight;
    }

    return height;
}