alpha buffer support

oh well this is prolly one stupid question but i was wondering if all opengl compatible cards DO support alpha buffer
i mean is it part of opengl 1.1 or is it just something that each single vendor can decide to support or not?
and, is trying to get a pfd the only way to test if a card supports alpha bits?

Yes, alpha is not guaranteed. You do need to query for it. Of course you should remember this isn’t just a per-card query. It is also controlled by what the present display mode is set to.