Well, assuming that you are using IIS and asp.net in the usual way, you should have an asp.net account under which the framework runs your application on your behalf.
The web application runs under one account, and through authentication users programmatically provides access to what your "main account" performs on their behalf.
Think about something like this ....
Asp.net downloads your application (asp account) User connects (iuser account) User logs in (depending on the account used, there may be auth windows or auth, ect forms)
A user asks to do something using your displayed web pages under their accounts ...
asp.net , (asp.net acount)
, asp.net ( asp.net)
...
asp.net, , .
... IIS /.
, ...
.
roleprovider , , ActiveDirectoryRoleProvider ActiveDirectoryMembershipProvider, AD DB asp.net.
, .