Given this website:

Is there anyone who can figure out what I've done so that my Firefox won't open the page correctly as in picture #1 and now it looks like picture #2. I swear I've done nothing, but I must have since it is messed up. It works in IE and in Opera like in #1.

Link #1 picture on the left side notice the side by side

Link #2 picture, no more side by side

much thanks for any attempts to help