Ok I saw this this morning but I had no time so I'm only looking at it now. Your using an id tag in the new page but it has no define CSS for it that's why its not showing up correctly in fire fox. Also there is another problem you are using absolute positioning to control the heading and content so I guess it still works but not my idea way to do layouts.
I've attached a screen shot in Firefox view with firebug. I checked the first style on your main page and just changed the id to that so its using that style 'new-content-main'
Yours is 'new-content-title' so either make a new style for that and adjust accordingly.
You will also have to adjust 'new-content' id as you can see in the screen shot its being effected as well but keep in mind if your other pages are using that same id it will be effected too so there it is I've pointed out the problem hope you can decide on a solution and have fun