I've been IE free since 2001 and I sure am proud of it
I've watched Mozilla grow so much....*sheds a single tear*....it's just beautiful
Anyway, it should be said that "Keeps HTML Formatting" refers to properly written HTML. If someone doesn't know how to properly code a webpage then there are no guarantees.
Either way, the key to trying out firefox is this: you must try it for a full week at least, and you must actively utilize the sources you have - such as mozillazine.org, TFP, etc - to ask questions when you're not sure about how to do something.
It's a different browser, and it's NOT IE, therefore, some things will be done differently. And if you don't ask how to do them, you'll never learn, and never learn to appreciate it.