storyday

force user login into wordpress only from one browser at the same time 
the last login action will kick out the already logged user 
this is a security plugin for wordpress,install this plugin to avoid simultaneously login

multi-login-checker

force user login into wordpress only from one browser at the same time

silver530

With this light-weight plugin, change WordPress login screen to white color to make it clearer.

White Login Screen

Change WordPress login screen to white color to make it clearer.

multi-login-checker vs White Login Screen