It seems that they are currently testing formatting of the blogs to be read more easily by mobile phone users. At present they don't automatically reformat for reading on a mobile phone which can make navigating the site a bit more cumbersome.
I've already noted from my stats that a significant percentage access this site by mobile so will be setting it up to be more easily read. If you want to do the same for your blog, here's how (if you don't already know):
- Go to Dashboard
- Access settings tab
- Click on email & mobile tab
- At the top of that page click next to the setting: "Yes. On mobile devices, show the mobile version of my template."
- Scroll to bottom of page and click "save changes" button
If you don't like it, it can be undone just by clicking on the no button