You're declaring @posts
twice in your controller. Try something like this:
if params[:tag]
@posts = Post.tagged_with(params[:tag]).order("title").page(params[:page]).per(3)
else
@posts = Post.order("title").page(params[:page]).per(3)
end
After removing the top @posts = Post.order("title").page(params[:page]).per(3)
line.