$(document).ready(function(){
    var $btn = $('.form_submit');
    var $form = $btn.parents('.form');

    $form.keypress(function(e){
        if (e.which == 13 && e.target.type != 'textarea') {
            if ($btn[0].type == 'submit')
                $btn[0].click();
            else
                eval($btn[0].href);
            return false;
        }
    });
});