Hi, we are using custom forms outside of Marketo. The basic idea is that you create a form in Marketo and you'll need that ID. Now just create a page with a form. Point the <form action="XXX"> to a script you create (e.g. in PHP or Javascript). That script will use the SOAP API or Munchkin API to associate the lead (http://community.marketo.com/MarketoArticle?id=kA050000000Kyr7CAC). In the API you can set that a form was filled and you need to supply the form ID.