If you're in a mobile device you're out of luck! Text entry is not done with a text-box or a text-area (the standard ways websites do text entry) so your browser doesn't know that it's time to open the virtual keyboard. In the future I'll add a keyboard for use in mobile devices. In the meantime, if your device has a way to manually open the virtual keyboard- use that!- the terminal will capture your keystrokes and register them as typing.