Here's a common pattern in my controller actions:

respond_to do |format|
  format.html {}
  format.js {
    render :layout => false
  }
end

I.e., if the request is non-AJAX, I'll send the HTML content in a layout on a brand new page. If the request is AJAX, I'll send down the same content, but without a layout (so that it can be inserted into the existing page or put into a lightbox or whatever).

So I'm always returning HTML in the format.js portion, yet Rails sets the Content-Type response header to text/javascript. This causes IE to throw this fun little error message:

Of course I could set the content-type of the response every time I did this (or use an after_filter or whatever), but it seems like I'm trying to do something relatively standard and I don't want to add additional boilerplate code.

How do I fix this problem? Alternatively, if the only way to fix the problem is to change the content-type of the response, what's the best way to achieve the behavior I want (i.e., sending down content with layout for non-AJAX and the same content without a layout for AJAX) without having to deal with these errors?

Edit: This blog post has some more info