Here's some ordinary body type, specified by CSS in the head to be 12px Georgia. The question is, does the tracking (horizontal spacing) of this type look normal to you? When I preview it, it looks fine in the following browsers:
But it looks much too tight (the letters crashing into each other) in:
To confirm my visual inspection, here's another test: I put a light gray border around the type column of these first few paragraphs, to make it easy to measure the width. If opened in both Mac Firefox and Safari, and an onscreen ruler is used to help resize both browser windows until the type measure (column width) matches, there are (at least on my Mac) more letters per line in Firefox than in Safari.
Here are two screenshots showing what the first paragraph of this Web page looks like on my Mac in the two browsers:
In Safari (very similar to the way it looks in Windows Firefox or in Windows IE):
In Mac Firefox:
See the difference? The Mac Firefox type is so tight that it's ugly and harder to read. It's hard to understand how this could be... if you look in the source code head you'll see that the CSS is really simple, with no letter-spacing specified. This page validated for both HTML and CSS at the W3C. And Safari and Firefox are (presumably) accessing the same Georgia font on my Mac. How could it look so much tighter in Mac Firefox?
By the way, the Arial caption above the screenshots is also tighter in Firefox... and, even stranger, when I tried using Geneva for the captions, it set tighter in Firefox and yet the caption somehow spilled over onto a second line anyway!
On your Mac, does the screenshot spacing match the real-type spacing? (Try resizing the browser window until the width of the gray border near the top matches the width of the gray border around the screenshots.) If you're seeing something different, perhaps it might have something to do with how the fonts are set up on my Mac... but even if that were true, since Safari and Firefox are accessing the same fonts on my Mac, shouldn't they render the same? Please let me know what you see, and what you think, in the Firefox Web Development forum, in the thread entitled Firefox type spacing: PC vs. Mac.
Thanks!