According to the settings tab on blogspot, if you leave a blank line between paragraphs, it will put in a paragraph mark. But it doesn't. It puts in a break mark instead, and in HTML, there is quite a difference between the two. Especially if you are using CSS (cascading style sheets).
Normally, this doesn't really have any impact. After all, the formatting in Cascading Style Sheets applies to subsequent paragraphs. The only place it doesn't cascade is after I've put in an image. I think the centering tag throws off the formatting.
And so, every once in awhile on Bloggity, the formatting looks really bad... but only on Internet Explorer. If everyone used Mozilla, it wouldn't be a problem.