customized landing page

[Riccardo Raichi]

hallo
google spreadsheet forms are great to deliver a landing page in minutes but 
the consequent thankyou page (i.e. the page you reach after submitting your 
data through the form) is not customizable (apart some text lines): no 
custom graphic, no google analytics code BUT I noticed some websites use a 
fully customized landing page and send data to google speradsheet 
(www.namalefiji.com for example): how do they do that? their thankyou page 
is fully customized
thank you