Hi! Thanks for reading. This post looks better in our award-winning app, Tips & Tricks for iPhone.
When typing an address in Safari, the period (full stop) key hides some alternative options. If you hold your finger on it for a second, a range of domains (such as .co.uk, .org, etc) will appear. Slide a finger to one and release. This only works when typing in web or email addresses, not when typing text in apps such as Notes or Messages.