Extra credit frame assignment

Ok i have a project for my internet programming class to make a tic-tac-toe board with frames. That is easy, the part that i dont know about is the extra credit. The professor will give us extra credit if we can have only boarders on certain sides of the frames so that it makes a tic-tac-toe board with the frame boarders. So some sides of the frames would need to have no boards and some would need boarders. Ive seen this done with css on tables but i dont know if you can do it with frames. If you know how or have an idea let me know. I need to get that extra credit:A+: