I had that happen a few times... not really sure what was the cause.
Im almost positive mine had to due with the photo view settings for this site. I had them loading at full resolution in stead of resized.
I would hit the back button an all of a sudden the whole page would be in bigger bold letters, hit forward and it would be fine. page zoom was not on either. it was only occasionally also.
but I did changed that setting and it hasn't happened since.
I think your freaking out man,,,