Are you looking on different computers and browsers, by any chance?
I don’t know if this is the culprit, but one problem I see with the fonts in your CSS is that you have specified fonts that not every computer may have, and no “fallback” fonts. Examples:
font-family: consolas;
font-family: constantia;
Constantia is a font that comes with Vista and Windows 7, so if you’re looking at your site on a Mac, for example, the browser won’t be able to display the site using that font, and will look for the next-specified font. As you haven’t specified any “fallback” fonts it’ll then look for the default font in the browser preferences. For example, I see the name at top left in Times New Roman, which is my browser’s default font, as I don’t have the font Constantia, which you’ve specified for h1 tags.
You normally specify fonts in “font stacks” with a common font listed first, which most computers will have.
Example:
font-family: Verdana, Helvetica, Arial, sans-serif;
I don’t know if this is the cause of the problems you’re seeing, but it’s something that jumped out at me when I looked at the code.
If you need further help, please post screen shots of the phenomenon you’re seeing.