# Rails 2 blog screencast, ajax error

**URL:** <https://www.ruby-forum.com/t/rails-2-blog-screencast-ajax-error/161966>\
**Category:** Rails\
**Created:** [March 4, 2009, 11:07am UTC](https://www.ruby-forum.com/t/rails-2-blog-screencast-ajax-error/161966 "2009-03-04T11:07:05Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![mdq](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/m/90ced4/32.png) [@mdq](https://www.ruby-forum.com/u/mdq)\
**Post date:** [March 4, 2009, 11:07am UTC](https://www.ruby-forum.com/t/rails-2-blog-screencast-ajax-error/161966/1 "2009-03-04T11:07:05Z")

</div>

I’ve been following the '15 minute blog ’ screencast on the rails  
site. Got to the part when you add ajax functionality to the comments  
form and when i try to post a new comment this way in Firefox, i get  
an alert window with the following message:

RJS error:

TypeError: null has no properties

and then, when i click ‘ok’:

Element.insert(“comment”, { bottom: “\<div class=“comment” id=  
“comment\_12”\>\n

\n **Posted less than a minute \nago\</  
strong\>  
\n rails \n**

\n\n” });  
$(“comment\_12”).visualEffect(“highlight”);  
$(“new\_comment”).resetlocal();

I’m pretty sure there are no typos in the code, I’m new to rails so  
any help is welcome. Thanks in advance