function ResizeBody()
{
    var header = document.getElementById("Header");
    var body = document.getElementById("Body");
    var footer = document.getElementById("Footer");

    var height = GetHeight() - header.offsetHeight - footer.offsetHeight;

    if (height > body.offsetHeight)
    {
        body.style.minHeight = height + "px";
    }
}

function GetHeight()
{
    if (window.innerHeight > 0)
    {
        return window.innerHeight;
    }
    else
    {
        return document.documentElement.clientHeight;
    }
}

window.onload = function()
{
    ResizeBody();
};