Open the following URL and select the View information  about site users   link in the Manage My Information category.

http://<servername>/sites/<sitename>/_layouts/1033/settings.aspx

https://i-share/sites/PO/_layouts/1033/userinfo.aspx

To delete  the user:
1. Open the site  in the browser
2. Choose Site Settings from the top nav
3. Choose Manage Users from the Administration section
(if its not there, your user  is configured by one of this site's
parent site)
4. Click the checkbox next to the user's name and choose Remove Selected
Users from the toolbar

To change the user's information:
1. Open the top-level site in the site collection in the browser
2. Choose View site collection user information  at the bottom of the
Site Collection Administration section
3. Choose the user to edit
4. Choose Edit User Information from the toolbar

i have one moe doubt. how to create a feedback box on the home page of a sub-site.