Mysterious black window?

Can someone tell me what this window is? There’s no header visible and no obvious controls available.

http://www.sightsea.com/extras/black_window.jpg

Thanks,
Steve

It’s Video Sequence Editor. Right click on one of its borders and select “add header”. It’s the same if you want to hide a header, right click on a border. This applies to all window types in blender.

The black one is the image preview window for the sequence editor. When you combine image/movie strips in the sequence editor you’ll see the results in that window. The online manual (Wiki) has an excellent description of the sequence editor written by PapaSmurf/RogerW. Check it out.

Thank you … both!