If you want your wordpress login and registration pages according to your wordpress theme and also some customizable setting example:email,security , then Theme my login wordpress plugin is useful for you. It replaces the wp-login.php file by using a page template from your theme and also includes a widget for sidebar login.
To customize login and registration page in wordpress
1. Download Theme My Login wordpress Plugin from this link.
2. Unzip and upload it to your WordPress wp-content/plugins directory.
3. Login to your wordpress admin. In your admin dashboard click plugins and activate the Theme My Login wordpress Plugin.
4. Then go to Settings menu and click Theme My Login Options.
5. Click modules and enable the your favorite modules and save changes.Then configure each modules and save the changes.
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Sample E-mail Module for user activation: