This page is used to manage Web Parts on a Web Part Page. It must be opened through a hyperlink with a query string that ...

This page is used to manage Web Parts on a Web Part Page.  It must be opened through a hyperlink with a query string that contains a URL to the Web Part Page, but the URL is invalid.  To open this page, open the Document Library that contains the Web Part Page, rest the pointer on the title, click Edit Properties on the Edit menu, and then click Open Web Part Page in maintenance view.