In the window itself is not clear, the text you can put enough (or very) limited and I'm not even sure it is displayed in all browsers. It is better to put it on the page with a link to this part and / or the ErrorDocument end (which appears if one cancels the authentication).
Well you can check in the doc / FAQ, ask for support, try the instructions associated with mod_auth_mysql:
Code:
AuthName "auth"
AuthType Basic
AuthMySQLHost server_name
AuthMySQLDB datab
AuthMySQLUserTable tablename
It AuthMySQLEnable
AuthMySQLNameField
AuthMySQLPasswordField password
require valid-user
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