Make textarea box wider?

I have a textarea that's very narrow.  I can make it wider by setting

'html' => 2

but I'd like to keep it as simple textarea, only wider.  Maybe I need to edit the css?  this is the code for the control:

'mycontrol' => array(
                    'type' => 'textarea',
                    'name' => 'mycontrol',
                    'html' => 0,
                    'caption' => _t('_caption_data'),
                ),

It depends on where the box that you want to edit is. Dolphin has tons'o'css files, the best way to figure out where to find what you are looking for is to use Firebug.