function isNumberKey(evt)
{
    var charCode = (evt.which) ? evt.which : event.keyCode
    if (charCode > 31 && (charCode < 48 || charCode > 57))
        return false;
    return true;
}      

function getWindowHeight() 
{
    if( typeof( window.innerHeight ) == 'number' ) 
    {
        //Non-IE
        nHeight = window.innerHeight;
    } 
    else if( document.documentElement && ( document.documentElement.clientWidth || document.documentElement.clientHeight ) ) 
    {
        //IE 6+ in 'standards compliant mode'
        nHeight = document.documentElement.clientHeight;
    } 
    else if( document.body && ( document.body.clientWidth || document.body.clientHeight ) ) 
    {
        //IE4 compatible
        nHeight = document.body.clientHeight;
    }
    return nHeight;
}