There appears to be a bug in Safari 4 running on Snow Leopard (MacOS X 10.6.1). Safari does not handle the <pre> tag correctly
The line below should look like this (the letters a-z all lower case):
But instead it looks like this:
For some reason various letters don’t show up. If you don’t see a problem then take a look at this screenshot:
Edit: I learned that the problem was that I had multiple versions of the Courier font installed on my computer. I used the Mac application, Font Book to remove the duplicate font and the problem went away.