Is [admin / admin] acceptable for all local websites?

As @montrealist says, using an insecure username and password combination on a local webserver installation that is not publicly accessible is not necessarily a security concern. If the server is publicly accessible, a secure username and password should be used of course.

How to protect wp-admin through .htaccess?

Basically, it should look like this: AuthType Basic AuthName NAME_THIS_THING AuthUserFile PATH_TO_USER_FILE <Files ‘*’> Require valid-user </Files> <Files ‘admin-ajax.php’> Allow from all Satisfy any </Files> Replace the upper case parts with something real. admin-ajax.php is the only file that should be available without restriction. The details of the user file are a little bit out … Read more

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)