What does this red minus overlay icon mean in Visual studio's Solution Explorer?

Question

What does this red minus flag mean in visual studio?

Answer 1

I believe this means the file is excluded from the build.

Note that this seems to be a bit different from "Exclude from project", in that the file shows up in the listing, but if you right-click on it and look at Properties > General, Exclude from build is set to Yes. If you set it to No, the red minus goes away.

One more datapoint, the project I imported started out as a VC6 project so this might be Visual Studio 2010's way of representing a legacy setting that was different than Exclude from Project.

The other comment about it indicating a missing item shows an exclamation point icon, not a minus.