hi everybody,
Iam using mysql.I have a login form in which user vl enter his name and password.Now when he/she types upper-case or lower-case in the username field,mysql unable to check the case.Is not mysql 4.0 not a case-sensitive.can anyone suggest how to solve it.

I don't know that there is anything to solve. If you are using the database for authentication, and the database is not case-sensitive in this respect, then that is just the way it is. Maybe if explain more clearly than "I have a ogin form and the DB is not case-sensitive". As you can see, from the summary of your post, tht those two things have nothing to do with each other, so we don't really know what your problem is. I can say however, that if you are not using at least MySQL 4.0, then you should update, preferably to at least 5.0 (if not higher).

Never seen a database where a where-clause on a string wasn't case sensitive.
If mySQL isn't, it's clearly not standards compliant (not surprising, I've known that for years) and a piece of rubbish (I've known that for years as well).

Use a real database engine like Firebird instead.