Same problems here. Thought it was Firefox only. Tried Chrome and same problem exactly as shown in first image above. Youtube does it, futureshop.ca and various other sites for me. It's a brand new 7 series Samsung laptop. This is my first experience using Windows 8 so I'm still in the learning stages but my PC knowledge is advanced and can't figure out yet what is causing this. Other references online had some suggestions (firefox settings, load pages automatically, font settings, etc) but none have worked for me.
I noticed some references regarding Norton, my laptop came loaded with it but I removed it right away (I use ESET) and even used the Norton tool to fully uninstall all traces of Norton. Could it have missed something since it's a relatively new OS?
For reference, I am running 3 extensions in both: lastpass, xmarks, and adblock but I tried disabling them in Firefox and the problem persisted.
This is frustrating.