Strange artifacts with Subsurf

I am a beginner and have been working on this model for quite some time. Recently I made some minor, but necessary changes around the eyes. I am attaching a screen cap of what has happened. If anybody knows how to fix this I would be most grateful! I can provide additional screen caps if requested, but I’m not sure what else you want to see.

Attachments


Remove any double vertices (Select vertices and W / remove doubles)
Remove any faces inside your mesh
Check for any non manifold edges (Select / Non Manifold menu in edit mode)

Drop down to lowest subdivision level so you can inspect your mesh. Are there ngons or triangles. if so change to quads. Can you see any other problems

If still not fixed attach or post a link to your blend file

Non Manifold edges helped me to solve the problem. I must have had a secret face behind the eyes that was messing me up. Thanks so much! I never knew about that trick.