Hide sub-forums

[Ninth Dimension]

Hi guys, I was wondering if you could help?

Take a look here: http://arathor.net/forum.php? - about half way down the page you can see the category 'Guild Forums' which is full of a ton of forums set-up by the various guilds that use the site.

As you can see, this is starting to take over a bit, so I wanted to hide it from view.

I know that I can choose to collapse it, and that sounds like a good solution to what I need, but how do I make it so it's collapsed by default?

Thank you