Can you provide specific URL's where you are having that issue?
Also, what screen resolution setting are you running?
Right-click the desktop and open Properties. Then open the Display Properties - Settings tab and look at the Screen resolution item. You should see something like 1280 x 768 pixels.

1366 x 768 Pixels is where I am. I am having the same issue with every website, including this one. The edge of my avatar (which should be on the far left) is about 1.5" from the left edge. The edge of where it says "subscribe to this page's feed", etc, is about 1.5" from the rt side. It only started when I downloaded Firefox. If I open something using Explorer, it displays just fine. The page is from rt edge to left edge. I can open Yahoo in both browsers and the Firefox side looks like a little sheet of paper laying in the middle of the screen with blank space on either side. Thank you so much for trying to help me!