In IE, your post is on the text editor mode as opposed to the "WYSIWYG" editor mode. You switch by hitting the button on the upper right that has two "A"s in it. The only problem is that box doesn't appear in your IE screenshot, only in the Firefox one, so I'm not sure how to fix it besides recommending you change browsers. Dreamer had the same problem, so it seems an IE compatibility issue that perhaps emerged with a recent browser update.