The .com button at the bottom of the Safari browser can be handy when typing in a web address. Just click it and the iPhone automatically adds the .com at the end of the address you just typed.
But what if the web address is a .net or a .org?
Just hold your finger on the .com button and get some alternatives for the .com address.
Pretty cool, this feature works on some other keys in the keyboard too, so experiment and see what other keys have dual features.