When I visit Stack Overflow and I've got the orange notification bar at the top of the page, there's a little "X" to close the bar. However, that X is not centered vertically within its box. This has bugged me for a long time and I figured it was a temporary thing. But it's never been fixed. Now I'm chalking it up to sloppiness.
As seen in Safari on Lion:
I've deleted Arial from my system (it's ugly).
On a stock install of Lion, I see a smaller font in Safari (though not perfectly aligned there either).
Any chance you're zoomed in, or have replaced some fonts? Or maybe your Apple's Arial has been replaced by a Microsoft version after installing Microsoft Office? (These fonts, incidentally, have caused much bigger issues.)
Actually, though the image is a bit a small to compare, it seems you're using Helvetica? That's odd, as that is not in the CSS, assuming it's Stack Overflow:
font-family: Arial,Liberation Sans,DejaVu Sans,sans-serif;
To see what font you're using: copy the text, paste into TextEdit, and then click in the text to see the font in the font dropdown. Mine says Arial, Bold, 17:
font-family, one should always put Helvetica, Arial, etc in such cases. Mac and iOS users get the better typography, and everyone else still gets what they would have got anyway: Arial.
font-family, like you've just proven yourself? Still you might want to vote for Why is Helvetica only used sometimes, Arial otherwise? then.
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