How to reproduce:
1. Open any Unity project
2. In the Project window, select any Asset
3. In the Inspector window, click the small button with the question mark

Expected result: the browser opens a Unity Documentation page with details about the Asset
Actual result: the link leads to a missing page

Reproducible with: 2017.4.40f1, 2018.4.23f1, 2019.4.1f1, 2020.1.0b12, 2020.2.0a14

Note:
1. The tooltip for the question mark button mentions opening the "reference" for the class, assuming the link was meant to lead to a Script Reference page, not the Manual.
2. This issue occurs with these Assets: Scene, Folder, Script, Shaders, Tile, Animator Override Controller, Timeline, GUI Skin, Brush.
3. This issue does not occur with these Assets: Assembly Definition, Audio Mixer, Material, Lens Flare, Render Texture, Lightmap Parameters, Custom Render Textures, Sprite Atlas, Sprite (Import Settings), Animator Controller, Animation, Avatar Mask, Physic Material, Physic Material 2D, Custom Font, Cubemap (Legacy), Terrain Layer.