ho risolto tutto con questo:

codice:
        private void Form1_Load(object sender, EventArgs e)
        {
            int BrowserVer, RegVal;


            // get the installed IE version
            using (WebBrowser Wb = new WebBrowser())
                BrowserVer = Wb.Version.Major;


            // set the appropriate IE version
            if (BrowserVer >= 11)
                RegVal = 11001;
            else if (BrowserVer == 10)
                RegVal = 10001;
            else if (BrowserVer == 9)
                RegVal = 9999;
            else if (BrowserVer == 8)
                RegVal = 8888;
            else
                RegVal = 7000;


            // set the actual key
            using (RegistryKey Key = Registry.CurrentUser.CreateSubKey(@"SOFTWARE\Microsoft\Internet Explorer\Main\FeatureControl\FEATURE_BROWSER_EMULATION", RegistryKeyPermissionCheck.ReadWriteSubTree))
                if (Key.GetValue(System.Diagnostics.Process.GetCurrentProcess().ProcessName + ".exe") == null)
                    Key.SetValue(System.Diagnostics.Process.GetCurrentProcess().ProcessName + ".exe", RegVal, RegistryValueKind.DWord);
        }