Inserted html using javascript function

I'm using a javascript function to insert html code into my page
(following the Railscast on nested models)

The function that inserts the javascript is this:

function add_result(link, association, content) {

  var new_id = new Date().getTime();
  var regexp = new RegExp("new_" + association, "g");
  var linkrow = $(link).up("tr");

  linkrow.insert({
    after: content.replace(regexp, new_id) });
}

And this is the html.erb that is inserted:

  <% for c in @picture_fields %>

    <% if c == "intervention" %>
      <tr class="pictureclass">
      <td class="name"><%=t 'form.results.picture.'+c%></td>
      <td><%= f.radio_button c,
t('form.results.picture.interventionoptions.option1')%><%=t
'form.results.picture.interventionoptions.option1'%><%= f.radio_button
c, t('form.results.picture.interventionoptions.option2')%><%=t
'form.results.picture.interventionoptions.option2'%><%= f.radio_button
c, t('form.results.picture.interventionoptions.option3')%><%=t
'form.results.picture.interventionoptions.option3'%></td>
      <td></td>
      </tr>

     <% elsif c == "couchetype" %>
      <tr class="pictureclass">
      <td class="name"><%=t 'form.results.picture.'+c%></td>
      <td><%= f.text_field :selected_couchetypes, :readonly=>true %></

      <td class="more"><%=
link_to( image_tag('more.png', :border=>0, :id=>"new_results_pictures_results_pictures_couchetype"),
{:controller=>"thesaurus", :action=>"list", :id=>"new_results_pictures_results_pictures_couchetype"},
{ :popup=>['thesaurus',
'height=800,width=750,location=no,scrollbars=yes']}) %>
     </td>
     </tr>

     <%else %>
       <tr class="pictureclass"><td></td><td ></td></tr>
       <tr class="pictureclass">
       <td class="name"><%=t 'form.results.picture.'+c%></td>
       <td><%= f.text_field c, :class=>"number"%></td>
       </tr>

     <% end %>

  <% end %>
       <tr class="pictureclass"><td></td><td><span class="right"><%=
f.hidden_field :_destroy %><%= link_to_function
t('form.results.picture.destroy'), "remove_fields(this,
'.pictureclass')"%></span></td></tr>

When the html is inserted, there is a size="30" attribute for the text
input field:

<input type="text" size="30" name="sample[treatments_attributes][0]
[results_pictures_attributes][1273597816957][couchenum]"
id="sample_treatments_attributes_0_results_pictures_attributes_1273597816957_couchenum"
class="number">

But I have no idea how it got there. Any ideas?