Formlets are a way of building HTML forms that are type-safe, handle errors, abstract and are easy to combine into bigger forms. Here's an example:
name :: XHtmlForm String name = input Nothing
The input function takes a Maybe String, and produces a XHtmlForm String. The Maybe String is used for default values. If you give it a nothing, it won't have a default value. If you pass in a (Just "value"), it will be pre-populated with the value "value".