Login into portal without Logon page

Dear Experts,

I have developed an html page to pass the user id and password to portal by using j_user and j_password.

Now all users are able to access portal content from this html page.

User enter the user id and password in that html page then user will enter into portal successfully without logon page.

If user enters wrong user id and password it is redirecting to portal logon page.

Is it possible to display the exception like "User authentication failed" in html page?

Please suggest me.

Regards,

Venu