I would reccomend avoiding frames. They actually don't look too bad in Firefox for me, but in ie it looks really bad at the moment. I'm seeing frame dividers, as well as GoDaddy ad frames (these may be adblocked in FF, I'm not sure honestly).

I would make the transition between the menu on the left, and the logo on the top left a little smoother, same as the transition from tartan on the left to page on the right.

I'd also chop the tartan on the left side at a different place (I'm seeing it in Firefox by the way), so that the image is smaller, and it repeats more smoothly.

Also, there's a typo on the "Kilts" page:

" The first thing I discovered is that they are incredibly comfortable. They are much cooler or hot days, and allow a better range of movement."

Also, It's very difficult to pull off a simple black background website, let alone one that's professionally oriented. Usually a white/light grey primary background will work better (for example, the background for all the content here is a light grey/light blue, and the secondary background is the tartan).

If you need help with anything let me know, I used to do websites as a hobby, and briefly for some work.