Creating pages inside of categories and Sidebar Changes

Hi,

I am creating my Blog manually, adding extensions and creating visual adaptation.

But I am with a problem.
It would like to know if it is possible to create a “Page” inside of a “Category”.
This would be of great utility for me, therefore it would go better to organize the structure.

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About yhe sidebar, I need to change to show the login form (of the wp-login.php) in the sidebar, including the Register link and the password remeber too.

Sorry but my English is very bad.
But I need help urgently.

Thanks