Microsoft Sharepoint is very vast software, It contains many software products like :
Microsoft Sharepoint Server
Microsoft Sharepoint Foundation
Microsoft Sharepoint Search Server
Microsoft Sharepoint Designer
Microsoft Sharepoint Workspace
So Microsoft Office Sharepoint Server that is also called MOSS, is one of software product in Sharepoint. Microsoft Sharepoint Foundation providing a web portal with commonly needed features. This includes a collection of web parts that can be embedded into web pages. So these web pages can be edited by Microsoft SharePoint Designer. Microsoft SharePoint Designer is a specialized web page editor for designing SharePoint sites.
Are you receiving the error “The URL ../../_catalogs/masterpage is invalid” when you try to check out a page using SharePoint Designer?
The default master page has not been set in the gallery.
The site masterpage url may point to a masterpage other than the correct one.
1. Using SharePoint Designer open your Top-level site
2. Locate the Master Page Gallery located: _catalogs > masterpage and find the default.master page
3. Right-click on the appropriate default.master file and click “Set as Default Masterpage”
4. Now try to open a page to edit and you will no longer receive this error!
But It is not sure that using these steps you can resolve this problem so in last you can use Sharepoint Recovery Software to resolve this error. The best Sharepoint recovery software is Stellar Phoenix SharePoint Recovery Software because it supports all latest version of Microsoft SharePoint Server like 2007 and 2010. It also have option to repair the whole SharePoint database or any single document from the SharePoint Server.