function CompatibleBrowser()
{
    var appVersion = navigator.appVersion;
    return (appVersion.indexOf('MSIE 6') > 0 || appVersion.indexOf('MSIE 7') > 0 || appVersion.indexOf('MSIE 8') > 0);
}

function BrowserControl()
{
    if (!CompatibleBrowser())
    {
        alert('Internet Explorer 6 or upper is required!');
        window.location='BrowserControl.html';
    } 
}
BrowserControl();