custom-login-portal_login-1.java

...
final String AUTH_FAILURE_PARAM = "authFailure";
final String AUTH_FAILURE_MSG_PARAM = "authFailureMsg";
...
if (StringUtils.isNotEmpty(request.getParameter(AUTH_FAILURE_PARAM))
    && "true".equals(request.getParameter(AUTH_FAILURE_PARAM))) {
    loginFailed = "true";
    if (request.getParameter(AUTH_FAILURE_MSG_PARAM) != null) {
        errorMessage = request.getParameter(AUTH_FAILURE_MSG_PARAM);
        if (errorMessage.equalsIgnoreCase("login.fail.message")) {
           errorMessage = "Authentication Failed! Please Retry.";
        }
    }
}
...
<% if ("true".equals(loginFailed)) { %>
    <div style="color: red; padding-top: 40px;">
        <%=errorMessage%>
    </div>
<% } %>
...