Apparently there’s no way to tell what version of Safari you’re running on your iPhone or iPod Touch. It’s not in the Safari app, nor in the Safari entry in Settings.
But you can type this into your Safari browser address bar:
Or, just click here (same thing),
Here’s what it looks like on my iPhone 4s (running iOS v6.1.2)
This show’s i’m running Safari v6.0.
Actually, this works in any browser. Eg in Firefox on Windows it gives this:
I got this tip from a tweet by Tim Acheson