We have routinely been making anti-matter for decades they were speculated to exist by Diarc 80 years ago. We even have a 3D periodic table to include them (http://www.physorg.com/news186931143.html) and have PET scanners for medicine based on them.

Its just normal matter with the charges reversed so an electron has a positive charge not negative etc.

Gravity seems to be a property of mass not charge so we expect anti-matter to still behaves the same way as matter does that is why anti-gravity is controvesial. In that we do not have a clear view on gravity one can speculate but personally it is unlikely though not impossible.

I believe in "Evil, Bad, Ungodly fantasy science and maths", so I am undoubtedly wrong to you.