Different Browsers Display Different Results

Since last publishing, now when I go to my site, newdawncommunities.org, the Top menu and footer vary according to browser.

IE 9 64-bit

last item on main menu goes to 2nd line
buttons in middle of page only partially show
page Title disappears from the page (flashes for a moment only)

IE 9 32-bit

All of the above same 3 problems

Opera 11.52

everything appears ok until any 2nd page is navigated to (link clicked on), then the footer bottom seems to fall out on that page and any other thereafter.

Firefox 5

last item on main menu goes to 2nd line

Google Chrome 15.0.874.106 m

All OK

Safari 5.1.1

All OK

Why are there display variations depending on the browser used, and how can I fix that?

Can anyone point me to any tutorial here that addresses this problem?

Thanks,
Ken