As discussed in a recent dev blog, we are introducing Single Sign On (SSO) to some of our websites and as of Monday April 22nd, Account Management will require SSO. 

As explained in the dev blog this does not affect your username and password; the change is simply that you will be directed to the new log in page which functions the same as the old one.

After logging in once you will not need to re-enter your credentials when you visit another EVE Online website that also uses SSO.