When I Open m Web sometimes it Takes "SHAREPOINT\system" Account insted of My Own Account.. Can anyone help me why it is doing like that?
In case any other internet wayfarers come by this problem; it's highly likely that this is due to the app-pool user being given the "Act as system" privilege in the Central Admin User Policy for the webapplication.
Probably one day we you enter the credentials you check the box to memorize it. To change this, on your computer go in Control Panel > User Accounts > Manage Windows Credentials. Then in the list look up for your server and the credentials that are set and delete them.
On the next prompt to SharePoint website you should be able to specify your own credentials and memorize them.
Central Administration-Security-Configure Service Accounts- change Farm Account in Network Service
Go to "log out" option or "Sign in as Different User", I think you have the information registered in your browser