As an additional security measure you can encrypt sensitive data in your database. When a hacker obtains access to your database, the hacker will find the encrypted data. You want your web application to enter new encrypted data into the database and you want to grant users of your web app access to the sensitive data without exposing the decryption key to the hacker.
When I was working on this blog (which is based on the Yii blog tutorial) I noticed that my pages included CSS files like pager.css and styles.css. Those files are registered to CClientScript by a widget. The CSS files contain rules for the layout of the widget. But I want full control over the layout of all element on my website from one CSS file so I had to disable the CSS of the widget.