Page layouts are great functionality that comes along with the Publishing Infrastructure in MOSS. They allow you to enforce a consistent structure and even consistent content in pages which you allow your users to create.
However, sometimes (due to the powers that be), you may have access to a site with pages based on page layouts with SharePoint Designer, but not the page layouts themselves. (The page layouts, are stored in the root web in the Master Page Gallery, along with the master pages, in the /_catalogs/masterpage folder.) When you try to edit one of these pages, you are informed that:
Each page in the Webs (sites) that you have access to which utilizes the Publishing Infrastructure will be based on one of those page layouts. You can’t edit the page layouts if you don’t have permissions on the root site. Q.E.D.
However, if you right click on the page in the Folder List, you should see an option to Detach from Page Layout. You’ll see this dialog pop up:
Assuming that you really want to do it, go ahead and say ‘Yes’.
Later you can Reattach to Page Layout, but frankly I haven’t needed to do this. I’ve read that you can do it with impunity and then you have your customized page with it linked to the page layout again. Changes that you’ve made to Web Parts in Web Part Zones will stay in effect but any other changes will be overwritten by the page layout. The dialogs then look like this:
However, you don’t have to reattach it. It will just mean that the page won’t reflect any changes to the page layout it was associated with in the future. Assuming this is OK, you’re good to go, but make sure that you document this choice, as it may become important later.