Captcha input box too long , affects page formatting

I have the same problem... :-/
Can't find how HTML for CAPTCHA is generated also...
Does anybody solved this problem?

'#required' => TRUE,
'#size' => 15,
'#validate' => array('_captcha_validate' => array())

note that, '#size' => 15, is added between the two arrays. it must be some where line ~145 or so.

are you using Math captcha, or Textimage captcha?

thanks, perfect, this is working (insert line 140):
$form['captcha_response'] = array (
'#type' => 'textfield',
'#size' => 10,
'#title' => t('Math Question: What is %problem?', array('%problem' => $x .' + '. $y)),
'#defaultvalue' => '',
'#description' => t('Please solve the math problem above and type in the result. e.g. for 1+1, type 2'),
'#weight' => 0,
'#required' => TRUE,
'#validate' => array('_captcha_validate' => array())
);