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Firefox3 can open multiple web pages stored in its toolbar at once, in the same way as on the previous version.
Firefox3 can open a group of web pages stored in its toolbar simultaneously, in the same way as on the previous version.
Firefox3 can open a couple of web pages registered in its toolbar all together, in the same way as on the previous version.

Are my sentences correct and natural to say?

Thanks in advance.
Comments  
Hi,

I would put 'all' in the one you wrote:
Firefox3 can open multiple web pages stored in its toolbar (all) at once, in the same way as on the previous version.

I am NOT sure this is what you wanted to say though.
Thanks, Anon.
All at once is better than mine!