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You can use your mobile internet to access Twitter.
Unless you have a mobile phone plan that supports Twitter, then yes, Twitter will charge you money.
It depends on your mobile phone plan.
By going to the Twitter mobile site on your phone.
Either a computer/laptop or a mobile phone.
It means you will receive texts (to your mobile phone) with updates.
Either a computer/laptop or a mobile phone.
A computer is the main device used for Twitter. However, mobile phones such as iPhones have a down loadable application that allows you to Tweet from your mobile phone.
As of July 2009, no.
Joining Twitter is free. As for mobile charges, it depends on your provider and your mobile plan. You should contact your provider to find out what you are and aren't charged for.
The phone should come with the app installed.
It depends on your mobile phone plan.