6 Sided Skybox now also has the additional properties Exposure and Rotation. These have to be included and explained in the Properties table and the screenshots have to be updated to include these as well: Editor/Data/Documentation/en/Manual/class-Skybox.html

This paragraph is also outdated: "You have two options for implementing Skyboxes. You can add them to an individual Camera (usually the main Camera) or you can set up a default Skybox in Render Settingss Skybox Material property. The Render Settings is most useful if you want all Cameras in your scene to share the same Skybox." - The scene render settings have been moved in the Lightmapping window.

"Unitys Standard Assets contain 2 pre-setup Skybox materials in Standard Assets->Skyboxes" - this is also not true anymore, since we ship different standard assets with Unity 5. They only have one Skybox and that one uses a Procedural shader. This in itself should probably also be explained in the manual. (The screenshot below this paragraph should be updated to show this new Skybox as well)

Also, the last Hint on the page is not true anymore: "
Its a good idea to match your Fog color to the skyboxs color. Fog color can be set in Render Settings." - Fog can be set in the Lighting window now
2. How we can reproduce it using the example you attached