## It's in haml, btw

## _product_description.haml
= f.text_area :description
#preview-link
  = link_to_remote 'Click to preview', :url => {:action => 'show_preview_description', :f => f}, :with => "'description=' + $('product_description').value"

## _product_preview.haml
= RedCloth.new(description).to_html

#preview-link
  = link_to_remote 'Close preview', :url => {:action => 'hide_preview_description', :f => f, :description => description}

## _show_preview_description.rjs
page.replace_html 'product-description', :partial => '/products/partials/product_preview', :locals => {:description => description, :f => f}

## _hide_preview_description.rjs
page.replace_html 'product-description', :partial => '/products/partials/product_description', :locals => {:description => description, :f => f}

## products_controller.rb
  def show_preview_description
    render :partial => '/products/actions/show_preview_description', :locals => {:description => params[:description], :f => params[:f]}
  end

  def hide_preview_description
    render :partial => '/products/actions/hide_preview_description', :locals => {:description => params[:description], :f => params[:f]}
  end