The Preview is not at all how it really looks!

So when I'm creating a post and use the little preview button to see if it looks ok or if I need to adjust where everything is located, you'd think that would be how it would show up on my blog right? Wrong!!!! Every time I've used the preview thing and had it how I wanted it it looks completely different and even messed up when I post it. Like the tour of our little apartment. It was exactly how I wanted it and everything was in the right spot and the narration was in the right spot. Well after the post it is completely off and the words don't go with the pictures and everything is messed up!!!! It's not a huge deal I just felt like venting about it. lol