What resolution is your monitor set to?
They aren't really columns, per se. Even if I removed the blue and left it as white, they would still show up as columns. It all depends on the resolution of your monitor. Those viewers with lower resolutions won't see anything. As for me, I have a widescreen monitor so I see more.
The main forum tables are set to a certain width. If I made the forum any wider, it would be more difficult for viewers to read because sentences would be too long.
How does it show up on your screen?