[Lynne]

Writing with black fonts on a black background is generally not a good idea if you want someone to actually read what you wrote.

Since I still have no clue what is up from your image, I will guess that you have not set the width to 100% (or similar) for your forum and that is what you are wanting. It's a custom style, so I don't know if it will take input from Style Manager > sTyleVars > Main Table Width, but you can try that. Otherwise, I seriously have no idea what you are wanting and unless I get a much better explanation, I'm gonna have to let someone else do the guesswork here.