function pageHeight() {

    return window.innerHeight != null ? window.innerHeight : 

        document.documentElement && document.documentElement.clientHeight ?  document.documentElement.clientHeight : 

        document.body != null ? document.body.clientHeight : null;

} 



function centerOnPage() {

    var tblMain = document.getElementById("tblMain");

    tblMain.style.height = pageHeight();

}