For the Symfony2 users out there, Dean Clatworthy has a handy tip to help you customize the output of your application a bit more - a method for styling the error messages coming from forms using a custom template.
I spent a large portion of my day today trying to customize the HTML produced by Symfony 2 for form errors. The documentation has a section on how to do this, but for the life of me, I could not make it work. Here is a working, re-usable solution.
His solution involves the creation of a template in your "/Resources/views/Form/" directory that contains a Twig template for the error set output. This is then applied in your view using an additional parameter on the error output tag, including this new template from the "Form" directory. This sort of styling could also be applied if you needed custom elements with their own layouts in your forms as well.