Is the Voodoo4 compatible with OpenGL? I looked on the 3Dfx website and it said that it is compatible. But when I looked on the list of compatible graphic cards with OpenGL, it listed all the other Voodoos except for the Voodoo4. Is it compatible or not?

Voodoo 4 is just like Voodoo 5, but with one chip. If Voodoo 5 is listed, Voodoo 4 should work just fine.