Hello,

•   I have read about how to configure My Sites SharePoint from "http://technet.microsoft.com/en-us/library/ee624362.aspx"
• I have read the following section : 

Perform these additional steps to configure permissions for users to create team sites from their My Sites to use site feeds

1. In the Policy group, click Permission Policy.

2. On Manage Permission Policy Levels dialog box, click Add Permission Policy Level.

3. Type a name for the permission policy.

4. Under Permissions, in Site Permissions, select the Grant option for Create Subsites - Create subsites such as team sites, Meeting Workspace sites, and Document Workspace sites.

5. Click Save.

6. In the Policy group, click User Policy.

7. On Policy for Web Application dialog box, click Add Users.

8. On Add Users, in Zones select (All Zones), then click Next.

9. In Choose Users, enter the user names of the users that you want to create team sites from their My Site to use site feeds. If all users can create team sites from their My Site to use site feeds, click the Browse icon. In Select People and Groups, click All Users, then click Everyone. Click Add, and then click OK.

10. In the Choose Permissions section, select the name of the Permission Policy created previously.

11. Click Finish, and then click OK.

• I have configure My sites in SharePoint . And I didnot  configure the previous step .
• Then I log in by a user . Then he created a personal site . Then He can create a sub site under it .

    So what is the previous section for ?