[Theme: twenty ten] Adjusting width of text widget

Hi there,

I have adjusted the width of the right hand side sidebar in (a child theme) of twenty ten to 300px.

Underneath the Facebook like box, I have added a banner in a text widget and was expecting to see it in 300px width as well….but I am not!

Can somebody please advise how to make sure the width of this text widget is displayed at 300px?

Thanks so much in advance!

This is the url to the page: http://www.musical-creations.com/english/