My computer adds a name for all sign in attempts for various web sites, Facebook etc.

How can I delete unwanted names?

I think it depends more on what browser you're using. I use chrome, and I know if I go into options and settings I can tell it to save or to not save things like user names, passwords, etc. I think Firefox has something similar but don't use it enough to be 100% sure. Also, some sites have the "remember me" box. If you don't click that, it shouldn't be saved.

Which browser are you using?