There are several problems. By several, I mean many.
You didn't post your head section, what does that and your doctype look like?
Ideally, you should be using an external stylesheet so the style applies to every page of your site and if you have to change anything, you only have to do it once. The link to that external stylesheet belongs into that missing head section.
I assume there are an opening and closing body tag that just wasn't included in the code you posted?
align="center" is deprecated. Instead, use your external stylesheet and write
h2 { text-align: center;}
No need for strong - h tags are bold by default, so defining them as strong is pretty much redundant.
<br />
Is a line break tag - it is not meant to be used to create space. If you want more space between you h2 and what's next, use your external stylesheet to add
h2 { margin-bottom: 15px;}
(of course the number of pixels depends on the amount of space you want)
Your navigation is a list and should be coded as such (with ul and li tags)
If you're floating somethign, you don't add line breaks - again, use the stylesheet to add margins or padding..
All your written detail should be inside paragraph tags (one paragraph at a time) - same goes for what's following your H3 Mission stuff.
You're also missing your div="main" closing tag, but maybe you just didn't copy/paste everything.
The above gives you
this - view the source to see exactly what I did.
Now just add margins or padding.
Also, it'd be good to wrap everything between the body tags into a wrapper division and style that to
#wrapper {
margin: 0 auto; (to center things)
width: 1020px; (or some other with)
}
To get your navigation list back into a line, see this:
http://how-to-build-...h-html-and-css/
Let me know if you have any questions.