URL Hack working for some fields but not others. Why?

Question

This should have taken me 5 minutes and after 1.5 hours of trying different things I still can't seem to understand why this url hack doesn't work

The code below just pre-populates the 1 contact 2 account 3 and the current user.

The first two work fine however the current user doesn't make it into the custom lookup field. I rechecked the ID of the field. It is correct. What am I missing?

/a07/e?RecordType=012w0000000iaZ9&nooverride=1&CF00N20000003NRbz={!Account.Name}&CF00N20000002kMy5_lkid={!Contact.Id}&CF00N20000002kMy5={!Contact.Name}&00Nw0000008ZPxv={!User.Name}&00Nw0000008ZPxv_lkid={!User.Id}

Answer 1

You are missing CF prefix for the user field..

hope this will work

/a07/e?RecordType=012w0000000iaZ9&nooverride=1&CF00N20000003NRbz=
{!Account.Name}&CF00N20000002kMy5_lkid={!Contact.Id}&CF00N20000002kMy5=
{!Contact.Name}&CF00Nw0000008ZPxv={!User.Name}&CF00Nw0000008ZPxv_lkid=
{!User.Id}