I haven't played with rounded corners in a while, and with all this new CSS stuff I may be unaware, but I remember rounded corners just being a picture.
Like if you had a big table, you would tack on an extra 4 cells somehow and have them hold a rounded corner each. In a thinner table, you can get away with just 2 pictures, each with 2 rounded corners..
You should be able to have rounded corners if you use background images in the links and menus - I haven't actually tried it, but I don't see why it wouldn't work.
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