I noticed for 2 or 3 weeks, the calendar of the profile page (when I click on the number of consecutive days I visited SO) is not correctly display on Firefox only. I don't reproduce the problem on Google Chrome for example.
Firefox 26.0, with no theme and no plugin, except HTTPS-Everywhere and All-in-One Sidebar, but I don't think they can have any connection with this.
Here is what I have on my Firefox :
I have reproduced this problem with my personal computer, and the the office's one (only with FF). I found on meta but didn't found any similar topic... Am I the only one to have this problem or is it a known bug ?