Hi Stephan,
I think see where you're confused. When you say "web form", you mean
HTML, right? Other people offered ASP.NET solutions cause there is also
something called a "Web Form" in that technology.
By default, web browsers send form variables as name/value pairs that
you're familiar with. What you need to is get those form fields into
XML for use with the Atom Protocol. You can do this two ways:
1.) Post the form to the server, and have the server convert it to XML
and contact blogger. Kind of using the PHP script as a hop.
2.) Use JavaScript to take the form values, convert them to XML, and
send them directly to the server. Lucky for you, Mike Davies has
already written this code and decided to give it away:
http://www.isolani.co.uk/blog/atom/JavascriptAtomApiClientUsingXmlHttpRequest
Good luck,
Robert Sayre