public void RegisterStyleSheet(string sheetURI, uint type)
        {
            nsIIOService ios = Xpcom.GetService <nsIIOService>("@mozilla.org/network/io-service;1");

            ios = Xpcom.QueryInterface <nsIIOService>(ios);
            nsIURI ssURI = ios.NewURI(new nsAUTF8String(sheetURI), null, null);

            if (StyleSheetService.sheetRegistered(ssURI, type))
            {
                return;
            }

            StyleSheetService.loadAndRegisterSheet(ssURI, type);
        }