The format of log records and pages is not constrained to follow the format of data pages.
http://msdn.microsoft.com/en-us/library/ms190925(SQL.90).aspx
One of the system pages stored in both the primary data file and the first log file is a database boot page that contains information about the attributes of the database.
ms-help://MS.SQLCC.v9/MS.SQLSVR.v9.en/udb9/html/39e00ebe-c9b7-4d53-90bd-15de2015fd34.htm
Best Regards,
Chris Büttner