[ubuntu] ?Are all graphics cards Linux compatable?

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http://ubuntuforums.org – Hey guys, I am new to the forum and new to Linux. I have about a 6 year old gateway desktop that I plan on putting Ubuntu on to play around with. It needs a new motherboard, processor, and graphics card. I just want a cheap graphics card for now as I won't be gaming or anything. My question is, many of the cards say windows 7 compatable but nothing about Linux. Are they all supported or are their certain ones I should use? Thanks! (Hardware)