Problem publishing Web Site

Question

Hi, This is the fiRst time I'm publising a Web Site and I get that error. I supposse that it's a problem with permissions. but I can found where. Any idea about what I have to do ????.. Thanks Euclides THIS IS THE ERROR............. [SqlException (0x80131904): Login failed for user 'NT AUTHORITY\NETWORK SERVICE'.] System.Data.ProviderBase.DbConnectionPool.GetConnection (DbConnection owningObject) +564 System.Data.ProviderBase.DbConnectionFactory.GetConnection (DbConnection owningConnection) +88 System.Data.ProviderBase.DbConnectionClosed.OpenConnection (DbConnection outerConnection, DbConnectionFactory connectionFactory) +106 System.Data.SqlClient.SqlConnection.Open() +112 System.Web.DataAccess.SqlConnectionHolder.Open (HttpContext context, Boolean revertImpersonate) +183 System.Web.DataAccess.SqlConnectionHelper.GetConnection (String connectionString, Boolean revertImpersonation) +152 System.Web.Security.SqlMembershipProvider.GetPasswordWithF ormat(String username, Int32& status, String& password, Int32& passwordFormat, String& passwordSalt, Int32& failedPasswordAttemptCount, Int32& failedPasswordAnswerAttemptCount, Boolean& isApproved) +797 System.Web.Security.SqlMembershipProvider.CheckPassword (String username, String password, Boolean updateLastLoginActivityDate, Boolean failIfNotApproved) +1878 System.Web.Security.SqlMembershipProvider.ValidateUser (String username, String password) +81 System.Web.UI.WebControls.Login.OnAuthenticate (AuthenticateEventArgs e) +158 System.Web.UI.WebControls.Login.AttemptLogin() +94 System.Web.UI.WebControls.Login.OnBubbleEvent(Object source, EventArgs e) +104 System.Web.UI.Control.RaiseBubbleEvent(Object source, EventArgs args) +35 System.Web.UI.WebControls.Button.OnCommand (CommandEventArgs e) +116 System.Web.UI.WebControls.Button.RaisePostBackEvent (String eventArgument) +137 System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEv entHandler.RaisePostBackEvent(String eventArgument) +7 System.Web.UI.Page.RaisePostBackEvent (IPostBackEventHandler sourceControl, String eventArgument) +11 System.Web.UI.Page.RaisePostBackEvent (NameValueCollection postData) +33 System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +4427