There's one point Glenn forgot to mention: GIF files support multiple "frames," which means they can be used for simple animation. I believe this feature is exclusive to GIF since, until Netscape supported it, no one had bothered with this rather obscure part of the GIF specification. PNG was designed before Netscape supported multi-frame GIFs, and the designers didn't see the point of supporting this completely unused feature. Pity.
Open URLs Quickly from BBEdit
If you're working on a bit of text (HTML or otherwise) in BBEdit, and you see a URL that you'd like to open, the fastest way is to Command-click it. Most BBEdit users probably already know this tip, but if you don't, it's a huge time-saver. (The same trick works in BBEdit's free little brother, TextWrangler.)
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