Ledufe,
just went to your site on IE and tried to register with the pop-up form. Everything is fine, but when I tried to sent the form, it wanted to sent it by starting my outlook mail client and as you can imagine, i had to cancel this -for me- undesired action. (i use outlook for business only!)
I don't know yet how to do it, but wouldn't it be better just to upload the data?
Edit:
1. from your source: you use the mailto: command, which opens the mail client associated with the browser. As I said, i never use that. Workaround: i will send the requested data via my anonymous gmail account to the mail adress given in the source.
2. I don't understand the advantage of your login form. Whats wrong with the one which is popped up by the browsers when using the standard ~login? It's much safer and again my eyes were hurt again when i entered a user:pass in the form and (fortunatelaty) IE refused to connect. The command line of the window shows
http://user:pass@ledufe......

see rejetto's comment above and also mine in the quoted posting.