Hey folks, I'm migrating a Website from Rails 2 (latest) to Rails 3 (beta2). Testing with Ruby 1.9.1p378 and Ruby 1.9.2dev (2010-04-05 trunk 27225) Stuck in a situation, i don't know which part will work well. Suspect yield is the problem, but don't know exactly. In my Layout Files I use the following technique quite often: app/views/layouts/application.html.erb: <%= yield(:sidebar) || render('shared/sidebar') %> For Example the partial look like: app/views/shared/_sidebar.html.erb: <p>Default sidebar Content. Bla Bla</p> Now it is time for the key part! In any view, I want to create a content_for block (optional). This can contain a pice of HTML etc. example below. If this block is set, the pice HTML inside should render in application.html.erb. If not, Rails should render the Partial at shared/_sidebar.html.erb on the right hand side. app/views/books/index.html.erb: <% content_for :sidebar do %> <strong>You have to read REWORK, a book from 37signals!</strong> <% end %> So you've got the idea. Hopefully. This technique worked well in any Rails 2.x Application. Now, in Rails 3 (beta2) only the yield Part is working. || render('shared/sidebar') The or side will not process by rails or maybe ruby. Thanks for input and time!