autofill overwriting username field

One of the annoying things about safari is that when I'm viewing a page with fields, safari always replaced whatever username is in the username field with mine regardless of what is already there. This is extremely annoying because say - for example i only want to change something of my profile but not my username. How do i configure safari to stop doing that yet not stop the normal autofill from happening?

For example my username here is kipper3d - so I'm looking at a page that has administrator in the username field already, but when i open the page safari automatically inserts kipper3d in that field. Often times it doesn't give me a change to see what it was before so when i save the profile it can be set correctly instead of with kipper3d. I use different usernames and passwords for just about everything and Safari drives me nuts with this bug!

Thanks,

John