front end users / self registration renaming input fields, why????

[gothikon]

Hi

I've recently set up a site using front users and the self registration module, so far so good...

The problem I'm having is I've added some Javascript to manipulate the form by prepopulating fields from a cookie. However, I recently discovered it wasn't working and when I viewed the source code I disocvered that the prefix for form fields had changed from m2_ to m6_

Can anyone explain how and why this happens? I can re-write my javascript but need to know why this is happening.

Thanks!