I was editing a post in this thread:
http://www.dakkadakka.com/dakkaforum/posts/list/294849.page
And when I was, I scrolled down using my mouse wheel and then the page seemed to lag and not move for a short time. Then the whole page scrolled down instead of the text inside the edit box and all the test was suddenly small. I also had another Dakka tab open, and when I looked at that, the text was small on that as well.
Note that when I was editing, I hadn't clicked the actual "edit" button, I was just "double-click" editing.