If you are using CQ5.5 SP1 and you edit the page properties in siteadmin, this may not work as expected. For example, vanity URLs added to the page properties may not work correctly.
The issue with the page properties occurs because the node jcr:primaryType gets changed from cq:PageContent into nt:unstructured, due to a change in the latest Sling POST servlet. The only way to avoid this node change with SP1 is to edit the page properties of a page using the sidekick within each page view.
This issue is resolved in CQ5.5 SP2.1, and later versions.
If you cannot update to SP2.1 at this time there is a workaround using an overlay which you can install to avoid this problem.
Download and install the attached content package (SiteAdmin.Actions.js-overlay_40752.zip), containing an overlay of SiteAdmin.Actions.js, which prevents the nodetype of the jcr:content node being changed to nt:unstructured. Once the package is installed, please make sure to clear your browser cache to avoid potential client-side caching issues.
After upgrading to SP2.1 be sure to remove this overlay.