It has been possible to add forms to sidebars in Sitemason templates
all along. However, once the form is submitted, the user is taken to a
confirmation page away from whatever page they were on. When it comes
to just a simple contact form or quick survey, it would be a whole lot
better to have the form submit (or show errors if necessary) in the
same location on the original page. It can be done with hacks like
using an iframe, but that has its drawbacks.

Chip Hayner of CentreSource just asked for a better way, so I added an
option to the Custom Form under the Customize Behavior tab. By
choosing "Submit to the page the form is on" under Form Action, your
form will stay on the same page. To see this option, you need to be
set to at least the Advanced user level in User Preferences.

Chip used the feature in Nashville Office Furniture's website to allow
people to submit info about projects. Since there are required fields,
you can just click "Submit" to have it return errors in place. If you
were to fill out the form (and please don't unless you really want to
submit a project), you would see the confirmation page in the same
location.

http://www.nashvilleofficefurniture.com/chairs

Originally posted in the Sitemason Developers Google Group on Thu, 06 May 2010