That's was a master touch! Finally I know the difference between:
- "~masterurl/default.master": the page will use the site master page in the every page in the SharePoint site except Publishing pages
- "~masterurl/custom.master": is used by Publishing pages
Publishing pages. These are a special type of page. They require the Publishing Features of MOSS, and so aren’t in WSS. Publishing pages have a content type, and always exist in the Pages library of a site.
Pages in SharePoint – Introduction