bool CanRewriteOutput(HttpContextBase httpContext)
        {
            if (!settings.IsHtmlRewritingEnabled) return false;
            if (!httpContext.IsHtmlRewritingEnabled()) return false;

            var statusCode = httpContext.Response.StatusCode;
            if (300 <= statusCode && statusCode < 400) return false;
            if (statusCode == 401) return false; // 401 gets converted into a redirect by FormsAuthenticationModule.

            return IsHtmlResponse(httpContext);
        }