Sublime Text 2: disable document preview
Solution 1:
This is called the "Minimap" in Sublime Text. To disable it, go to View -> Hide Minimap in the menus.
Solution 2:
If you'd like a keyboard shortcut to toggle this, you can create one by adding this:
{ "keys": ["ctrl+k", "ctrl+m"], "command": "toggle_minimap" }
...to your Preferences -> Key Bindings - User file. This sets it to the sequence Ctrl+K followed by Ctrl+M, which I chose just because it's similar to the shortcut (Ctrl+K, Ctrl+B) which toggles the sidebar, but you can set it to whatever you like.