I just noticed this little tidbit and figured I would pass it along. When customizing sites in WSS v2 I made a habit of duplicating and renaming the default.aspx file for disaster recovery purposes.
MOSS 2007 makes use of the ASP.NET 2.0 feature of “Master Pages” – basically a master page sets the stage for the look and feel – headers, menu’s footers etc. You then create content pages that “inherit” the master page and hence follow a consistent look/feel.
Thing is though – if you were to open a .master page in SharePoint Designer 2007 and rename it – SharePoint Designer 2007 is smart enough to go to those content pages and change the reference to the master page.
Something to keep in mind, if you thought you done well be backing up your default.master and have been making changes to a new one, your content pages may still reference your backed-up .master page.
A real case scenario (happened to me 5 minutes ago)
While customizing a publishing site just now, I renamed my TopNavFlyouts.master to ORIGINAL-TopNavFlyouts.master and *THEN* duplicated it renaming it back to TopNavFlyouts.master. The content pages were changed when I renamed the page to reference ORIGINAL- so I wasn’t seeing my changes take place.
Hopefully this will save you a grey hair.