_new_activity.html.erb

 <%= form_for [@company, @activity], :remote=> true, :validate => true do |f| %>

 <%= f.label :title %>
 <%= f.text_field :title, :class => "input-width bottom-border"%>
 
 <%= f.label :background %>
 <%= f.text_area :background, :class => "area-height area-width bottom-border" %>

 <%= f.collection_select(:activity_category_id, ActivityCategory.all, :id, :activity_category) %>


 <%= f.submit "Add activity", class: "btn submit-deals" %>
 <% end %>

_new_deal.html.erb

 <%= form_for [@company, @deal], :remote=> true, :id => "form", :validate => true do |f| %>
 <%= f.label :name %>
 <%= f.text_field :name, :class => "input-width", :autofocus => true %>

 <%= f.label :value %>
 <%= f.text_field :value, :class => "input-width" %>
 
  <%= f.label :currency %>
 <%= f.text_field :currency, :class => "input-width" %>

 <%= f.label :background %>
 <%= f.text_area :background, :class => "area-width area-height" %>
  
 
 <%= f.submit "Add this Deal", class: "btn submit-deals" %>
 <% end %>





 

activity.rb

class Activity < ActiveRecord::Base
  attr_accessible :activity_category_id, :background, :title, :user_id
  belongs_to :company
  belongs_to :contact
  belongs_to :activity_category

  validates :company_id, :presence => true

  validates :title, :presence => true,
  					:length => {:minimum => 1, :maximum => 20}

end

deal.rb

class Deal < ActiveRecord::Base
  attr_accessible :background, :company_id, :currency, :deal_category_id, :deal_status_id, :name, :offer, :user_id, :value, :status, :state
  belongs_to :company
  belongs_to :deal_catergory
  belongs_to :deal_status
  belongs_to :user

  validates :company_id, :presence => true

  validates :name, 	:presence => true,
  					:length => {:minimum => 1, :maximum => 20}

  validates :value, :presence => true,
  					:numericality => true


end

gistfile1.txt

Uncaught TypeError: Cannot read property 'validators' of undefined 
_ref.focusout.ClientSideValidations
jQuery.event.dispatch
elemData.handle
jQuery.event.trigger
jQuery.event.simulate
handler