Main columns in IE not displaying correctly

[Guest smartlifestore]

I'm having problems with the way my website is displaying certain pages in Internet Explorer. When I use Firefox, the pages are displayed correctly, even though they are too wide for the screen and I have to scroll over to see the right side. My concern is when using IE, some of my pages don't display correctly at all. Some pages work fine, but on others the center column seems to extend too far to the right, even though the content doesn't move, it just leaves a blank spot on the right side, then the column that should be in the upper right is pushed down to the bottom right side of the page and it really looks bad. What can I do to limit the size of the colums so that every page fits correctly on the screen? I've been playing around some with the code, but am not having much luck. I tried to change the position of the column from relative to absolute, and that fixed the problem for the most part in IE, but then when I went back to Firefox, it was all screwed up with the right column on top of the center column. I tried changing column widths, but that hasn't helped either. I'm not a programmer, but I have to assume that there is some easy way to fix this, I just don't know enough to figure it out on my own.. Any ideas would be appreciated. My website is www.smartlifestore.com. My homepage displays fine, but if you look at some of the other pages, you'll see what I mean. Thanks for any help anyone can give me.