If the browser isnt supporting the new css3 propertys they will just get ignored, so there wont be any layout problem. Optional, i think you should include that CSS3PIE Project if the forum owners wish so that their users have rounded corners into IE Browsers also.

I dont think you should worry how they see it in IE anyways..... Experienced users will use modern browsers and not IE, If they are un experienced with the web then its their loss, as always with un experienced people
