gehenna: Do you have swipe keyboard navigation enabled? What browser are you using? Perhaps there is keyboard gesture control built into the browser that you're unaware of and triggering by mistake.

I do, because I have used Swype keyboards on Android for so long that the idea of typing individual letters seems positively ancient now - like dragging out an Imperial and changing the ribbon!

Safari and possibly. Gestures on phones are annoying other than pinch to zoom but Apple seems obsessed with some that are getting like playing Twister with your fingers. "To go back, touch the screen with a thumb and 3 fingers, swirling them in a clockwise motion whilst spreading them wider then bringing them together and saying "Abra Cadabra". I jest but you know what I mean.

Also - is it me, or is the spelling/word choice accuracy on the iOS swipe significantly less accurate than it is in Android?