Copy the URL and paste it in Twitter.

If your asking about general sharing, Firefox OS don't have that option right now.

If your asking about a website, then you contact the website administrator

But there's no copy/paste support in ffos.

Which mobile are you using? Geekphone/ZTE or anyother

Alcatel one touch fire

Maybe in 2.0?

The option to copy and paste is currently not available in Firefox OS. Our developers are working hard to make this possible in the upcoming release version.

Thank you for your patience, sorry for any inconvenience and thank you for contacting Mozilla Support and choosing Firefox OS.

This sounds like it would make a good project for an add-on, but I don't know whether Firefox OS browser supports add-ons.