Looking for logging into the User Button site and are not getting the correct working link for it? In such a case, you can use the links given here by searching your desired login page in the search box. If the page is present on our website then you will get all the links related to the User Button site. After that you can login as usual with your login credentials.
https://www.w3schools.com/howto/howto_css_login_form.asp
https://salesforce.stackexchange.com/questions/204286/why-cant-i-see-login-button-on-user-record
https://www.flaticon.com/free-icon/user-login-button_17547
https://www.flaticon.com/free-icons/user%20login%20button
https://developers.facebook.com/docs/facebook-login/web/login-button/
https://developer.salesforce.com/forums/?id=906F0000000ArT8IAK
https://developer.salesforce.com/forums/?id=9060G000000XhnCQAS
https://en.wikipedia.org/wiki/Login
https://stackoverflow.com/questions/20800736/attributes-for-login-button-in-login-form
https://uxplanet.org/designing-ux-login-form-and-process-8b17167ed5b9
https://developers.google.com/+/web/signin/
https://www.freepik.com/free-photos-vectors/login-button
https://help.duda.co/hc/en-us/articles/229321827-Adding-an-eCommerce-Store-Login