What does "Unauthorized zone" mean when browsing xsd files with Visual Studio 2010?

For me it worked after going to the properties of the XSD file and clicking on Unblock. i got this answer from How do I modify my settings to allow VS2010 to load 3rd party XSD files from the "Unauthorized Zone"?

Visual Studio caches XSD schemas at %VsInstallDir%\xml\Schemas with Target Namespace attribute (url of schema file) when you add them to your editor.

Blog post says that
The inclusion of Local.xsd in the “Unauthorized Zone” and the warnings in the error pane about not being able to resolve the schema location are an indication to the end user that the schema they were visiting attempted to bring in a schema from a zone that it is not authorized to access.

Reason the IO Permission error shows itself is your machine has no authority to download external xsd file(s) from the location.So there is no cache that Visual Studio might validate your other xsd files.

You should check your networking options so you may download those xsd files.While you can it means you have access to that location,so Visual Studio can cache them.If you're sure that you have access,you may also download those xsd files and put them Visual Studio's default schema location and indeed add them in editor.

Also check about cache here

Hope this helps
Myra