SQL & PL/SQL

Hello All.

I have pl/sql stored procedure generate html page. The page has form and I capture user name and password and submitted to the same stored procedure. I need to validate the user name and his password against my database. If the user exist in my database and supply the correct password then the procedure will do some jobs otherwise the procedure will return unable to login to the database error message because the user name or password incorrect.

So the question is
How to validate a give user and his password exist in the database?


Thanks.