sa 用户登陆失败什么原因

用户 'sa' 登录失败。说明: 执行当前 Web 请求期间，出现未经处理的异常。请检查堆栈跟踪信息，以了解有关该错误以及代码中导致错误的出处的详细信息。 异常详细信息: System.Data.SqlClient.SqlException: 用户 'sa' 登录失败。源错误: 
行 33:  SqlDataAdapter ST_cmdCmd = new SqlDataAdapter(ST_cmd_sql,ST_myConn);
行 34:  DataSet ST_classds = new DataSet();
行 35:  ST_classCmd.Fill(ST_classds,"类别列表");
行 36:  DataSet ST_cmdds = new DataSet();
行 37:  ST_cmdCmd.Fill(ST_cmdds,"推荐文章");源文件: d:\Documents\Visual Studio 2010\Projects\myBLog\BlogIndex.aspx.cs    行: 35 堆栈跟踪: 
[SqlException (0x80131904): 用户 'sa' 登录失败。]
   System.Data.SqlClient.SqlInternalConnection.OnError(SqlException exception, Boolean breakConnection, Action`1 wrapCloseInAction) +5295167
   System.Data.SqlClient.TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj, Boolean callerHasConnectionLock, Boolean asyncClose) +242
   System.Data.SqlClient.TdsParser.TryRun(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj, Boolean& dataReady) +1682
   System.Data.SqlClient.TdsParser.Run(RunBehavior runBehavior, SqlCommand cmdHandler, SqlDataReader dataStream, BulkCopySimpleResultSet bulkCopyHandler, TdsParserStateObject stateObj) +69
   System.Data.SqlClient.SqlInternalConnectionTds.CompleteLogin(Boolean enlistOK) +30
   System.Data.SqlClient.SqlInternalConnectionTds.AttemptOneLogin(ServerInfo serverInfo, String newPassword, SecureString newSecurePassword, Boolean ignoreSniOpenTimeout, TimeoutTimer timeout, Boolean withFailover) +317
   System.Data.SqlClient.SqlInternalConnectionTds.LoginNoFailover(ServerInfo serverInfo, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString connectionOptions, SqlCredential credential, TimeoutTimer timeout) +889
   System.Data.SqlClient.SqlInternalConnectionTds.OpenLoginEnlist(TimeoutTimer timeout, SqlConnectionString connectionOptions, SqlCredential credential, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance) +307
   System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, SqlCredential credential, Object providerInfo, String newPassword, SecureString newSecurePassword, Boolean redirectedUserInstance, SqlConnectionString userConnectionOptions) +434
   System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, DbConnectionPoolKey poolKey, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection, DbConnectionOptions userOptions) +225
   System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnectionPool pool, DbConnectionOptions options, DbConnectionPoolKey poolKey, DbConnectionOptions userOptions) +37
   System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnectionOptions userOptions) +558
   System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnectionOptions userOptions) +67
   System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection) +1052
   System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal& connection) +78
   System.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection owningConnection, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal& connection) +167
   System.Data.ProviderBase.DbConnectionClosed.TryOpenConnection(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions) +143
   System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource`1 retry) +83
   System.Data.SqlClient.SqlConnection.Open() +96
   System.Data.Common.DbDataAdapter.FillInternal(DataSet dataset, DataTable[] datatables, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior) +121
   System.Data.Common.DbDataAdapter.Fill(DataSet dataSet, Int32 startRecord, Int32 maxRecords, String srcTable, IDbCommand command, CommandBehavior behavior) +316
   System.Data.Common.DbDataAdapter.Fill(DataSet dataSet, String srcTable) +86
   BlogIndex.Page_Load(Object sender, EventArgs e) in d:\Documents\Visual Studio 2010\Projects\myBLog\BlogIndex.aspx.cs:35
   System.Web.Util.CalliEventHandlerDelegateProxy.Callback(Object sender, EventArgs e) +85
   System.Web.UI.Control.OnLoad(EventArgs e) +74
   System.Web.UI.Control.LoadRecursive() +120
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +2819