The site is not valid. The 'Pages' document library is missing.

The site is not valid. The 'Pages' document library is missing.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: Microsoft.SharePoint.Publishing.InvalidPublishingWebException: The site is not valid. The 'Pages' document library is missing.

How to fix the problem?
To fix the issue it is required to update the value of the __PagesListId property value to match the ID of the Pages library.

This can be done (e.g.) through the following Powershell script:
$web = get-spweb http://site-collection/path-to-affected-site
$correctId = $web.Lists["Pages"].ID
$web.AllProperties["__PagesListId"] = $correctId.ToString()
$web.Update()

Reference: http://blogs.technet.com/b/stefan_gossner/archive/2011/09/15/common-error-the-site-is-not-valid-the-pages-document-library-is-missing-error.aspx

Issue: Anonymous access site kept throwing 401 Resolution: View a list of all unpublished or checked out items

Issue:
 
Recently I had an issue where an anonymous site kep asking for user credentials, which was weird because the web app was set to anonymous and other sites did not prompt for authentication.

Resolution:

Turns out there were a lot of items that did not have a publsied version or had it checked out and were in draft state.

To find all unpublsied or draft versions:

Nagivate to "Manage Content and Structure > View: All Draft Document"

There are other various view that can help namely:

"Related Resources" - Which highlights all the other fiels that might have been checked out.


 

Quick Launch links randomly disappear SharePoint 2010

Issue:

Recently a client had complained that the navigation items under current navigation (quick launch) in a sub site where disappearing. The user was removing them and it looked as if they were just dropping out. If the user went back and added those items again, then they appeared under quick launch


Resolution:

This solution posted at [1] seem to help a few so will try this fix:

1. On the parent site of the site having the problem, create a “dummy” document library and leave the “Display on Quick Launch” option set to “Yes”. Once the library has been created, remove permission inheritance for the document library and the problem will be resolved for all sub-sites underneath this parent.

Yet to try out this option as the client had just added the navigation items back in, waiting for this to happen again so can apply this fix. Will update this post if Option #1 works for me


Ref:
 [1] http://social.technet.microsoft.com/Forums/pl-PL/sharepoint2010setup/thread/4439a80d-8e3e-4795-a21f-e63c221ed06b