For the Notifications Mute feature in Special:Preferences.
**Problems**
* If a username is typed (not selected from the list), the 'Save' button is active and can be clicked, but the username will not be saved.
* If a non-existing username is typed, the 'Save' button is active and can be clicked, but the user name is not saved. In this case, the message to the user, e.g. "the entered username does not exists" will be helpful.
** It is worth noting that there is no username validation when a username is 'entered'
**Proposed solution A**
* If a username is typed but not 'entered' (e.g., hit the return key) then display an error to users when they slick 'Save'
**Proposed solution B**
* If the username typed but not 'entered' is validbut not selected from the list, save it to the Mute list.
* If the username types'Save' but not 'entered'ton is invalidactive, display an error message
**Proposed solution C**
* If the username typed but not 'entered,' save it to the Mute list regardless if it is valid or invalidbut the input is thrown out.
**Existing error screenshot**
{F9210119}Solution**
* If a username is typed but not 'entered' (e.g. hit the return key) then display an error to users when they slick 'Save'.