Well the link works now; your browser will make no difference with links (IE accepts backslashes and a few invalid URIs but for the most part it's all the same). I was getting a 404/DNS error before when I first posted, but now I can see it. The problem is that you are using a Flash menu and I don't know how to (actually it's probably impossible) to target links with Flash. I'm not sure how it handles links, but the <base target="main"> in your sidebar frame might still work. You should try.
If you are looking for an easy frame editor, I believe MS Frontpage 2003 came in your kit; it will certainly be able to visually (What You See is What You Get) change any aspect of your frames, including width and background colour. There are also free WYSIWYG editors all over the internet that allow you to edit pages as you would a Word document for example. I suggest Frontpage 2003 as it can produce cross-browser code fairly well.
I am assuming you want to use frames for some design reason right? If not, I would actually suggest you stray from them. I find they are usually more trouble than they are worth.
But these [
1,
2,
3] might help you...