The drop down list you are seeing is what your Browser has remembered.
When it sees that you are doing a "log-in", it asks if you want to save the information. The web site can also indicate that you want to log-in automatically but that is actually a separate function.
What usually happens is that the user types in the name they think is the correct ID for the web site. The Browser then asks if it is to remember it. The user says "Yes". They may also have checked a checkbox that says to the web site to log-in automaically.
If the words they typed were correct everything is fine.
If they were wrong about either the User ID or the Password then the Browser has remembered the wrong info. But the web site has not remembered to do the auto-log-in because there is no known user there. So the site says, "I don't know you, try it again."
The question is, "which one is wrong; the ID or the Password?"
Let us first assume the Password was wrong, most of us might make that assumption at first.
So we eiher retype the same ID or maybe the browser (or the web site) has pre-entered that one piece of "known" (?) data in, and we tab to, or click in, the Password entry box and type the Password over again. The Browser then recognizes that the user ID is the same, and maybe even the Password is the same so it makes no comments or requests to the user and just passes the info to the web site. If the Password is different the Browser will ask you if you want to remember this new Password with that user ID. If it is now correct, the web site accepts it and all is well, otherwise we are back to square one, with one ID and Password remembered, maybe one or both in error.
Let's assume the user ID was wrong. So you give up retyping the password and/or trying different passwords trying to get in and decide to try a different User ID. The browser then sees a new ID and Password and asks the user if it should remember them. And the rest of the scenario repeats... But now the browser has remembered TWO user IDs and Passwords.
I have some web sites where I have tried several IDs and Passwords before I got the correct ID and password and all of them are "remembered" by the browser and ALL appear in the dropdown list.
To make matters worse, I have forgotten that the dropdown list exists and have again typed in the User ID and made yet another mistake and now there is yet another ID/Password pair in the list along with the correct one.
When I do remember that there is a list, the "correct" one is not the one on the top or on the bottom of the dropdown list! Ratzle-frazzle-frizzle-frazzle!!!!
Unfortunately, I know of no software that will let you edit that list to remove any single names for any particular web site but maybe FireFow will.
You can, via a utility built-in to the browser and/or via any of several anti-virus/-spam/-phishing/-spyware/-etc. programs, remove ALL user IDs and Passwords for ALL websites... but that is a bit drastic!!!!
Do you remember ALL the user IDs abd Passwords for ALL the websites you regularly (or seldom!!!!) visit?
Probably NOT! Thus wiping everything out is usually counter productive!
I used to have SEVERAL websites that I visit with SEVERAL user IDs and Passwords remembered in error. Then I ran a "clean-up" program that unknownst to me, erased all those entries. At first I was a bit upset (to say the least), but now I have been rebuilding those lists by going to all the web sites to log-in and each time I now do it this way.
Log-in using the best guess for the ID and Password, but when the Browser asks if it should remember them I say "NO!". IF the log-in works I log-out and re-log-in using the same ID and password and tell the Browser to remember them. If it does NOT work then I try another (and another and another!!!) always answering that question with "NO" until I do get it right and then I log-out and Log-in and have the Browser remember only the good pair. (I am still working on a couple of web sites!)
