Can not call RJS and throwing error

I created controllers of project and task and appropraite html pages for them and created two partials of fields and tasks and having link in fields partial, when i call it it is throwing RJS error, please find the code below and mention a solution for geting text box dynamically....

My Html page

<% form_for :project, :url => projects_path do |f| %>   <%= render :partial => 'fields', :locals => { :f => f } %>   <p><%= submit_tag "Create Project" %></p> <% end %>

Fields Partial

<%= error_messages_for :project %> <p>   Name: <%= f.text_field :name %> </p> <div id="tasks">   <%= render :partial => 'task', :collection => @project.tasks %> </div> <p> <%= link_to_function('Add') do |page| page.visual_effect :highlight, 'tasks' end%> </p>

Task partial

<% @task = task %> <%= error_messages_for :task %>

<div class="task">   <% fields_for_task(task) do |task_form| %>   <p>     Task: <%= task_form.text_field :name %>     <%= link_to_function "remove", "$(this).up('.task').remove()" %>   </p>   <% end %> </div>

My controller

class ProjectsController < ApplicationController

def index @projects = Project.find(:all) end

def new   @project = Project.new   @project.tasks.build end

def create   @project = Project.new(params[:project])   if @project.save     flash[:notice] = "Successfully created project and tasks."     redirect_to projects_path   else     render :action => 'new'   end end

def edit   @project = Project.find(params[:id]) end

def update   params[:project][:existing_task_attributes] ||= {}

  @project = Project.find(params[:id])   if @project.update_attributes(params[:project])     flash[:notice] = "Successfully updated project and tasks."     redirect_to project_path(@project)   else     render :action => 'edit'   end end

end