S**t - I just typed a whole big screed in explanation and ZAP! it was gone.
Anyway I will explain in a shorter version this time.
The ‘Fixed in Window’ positioning that you have used on the header is fine - but - as your page is centre aligned different widths of browser window will move your ‘Page’ relative to the header. Try adjusting the browser width (in any browser) to see them dance! It is not a Safari vs Exploder vs Firefox thing.
If you want to use this method then left align your page.
But I really don’t see the design advantage you are getting as your pages are very short anyway. And you shouldn’t Fix items that really should be part of your page content the way you have done your navigation!
By all means fix that at the top or left side but it looks daft in a resized (width) browser window.
And besides at 900px wide your site is considered width challenged
in these days of 1024 x whatever monitors and above.
I can’t see that really. There’s no compunction to make a site fit a
whole screen, no matter how wide the screen; personally, I don’t see
how screens getting bigger affects site design at all. For years I
designed at a maximum of 640 wide, often still do, although I’m more
likely to go to 800 these days. But when I do, I sometimes find it
hard to keep lines of text below the magic 80-100 character length,
and I find myself making design decisions that don’t necessarily suit
the site, just because I don’t want long lines of text, which is
difficult to read—sticking unecessary images in, just to shorten the
line length, that sort of thing. With the current trend for
horizontal menus and no sidebar, the problem gets worse …
I do believe that bigger isn’t necessarily better.