Forms Width where to edit it?

Hi! can you please help to know where is the exact path to edit the forms width, my site <!-- w --><a class="postlink" href="http://www.asesoresdinamicos.cloudaccess.net">www.asesoresdinamicos.cloudaccess.net</a><!-- w --> has a problem with right menu columns format, and I'm almost sure that is related to forms width.

So please help me to find the exact path to edit the forms width, please, please

I really appreciate your help

Ivan