Can't Acces

my colleague is using visual studio (VB) and making windows applications. we used same connection string but i can't connect to the sql server.

i am using visual studio(2003) .net(C#) and making web applications. this is the code.

System.Data.SqlClient.SqlConnection conn = new System.Data.SqlClient.SqlConnection ();
// TODO: Modify the connection string and include any
// additional required properties for your database.
//conn.ConnectionString = "integrated security=SSPI;data source=cerebrum;persist security info=False;initial catalog=dals";
conn.ConnectionString="Server=cerebrum;Initial Catalog=dals;User Id=sa;";
try
{
conn.Open();
// Insert code to process data.
Label1.Text="Connection successful";
}
catch (Exception ex)
{
throw ex;
}
finally
{
conn.Close();
}

and i'm getting this error
SQL Server does not exist or access denied.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.Data.SqlClient.SqlException: SQL Server does not exist or access denied.

Source Error:


Line 91: throw ex;
Line 92: }
Line 93: finally