Have it all set up again after some problems:
I was warned in myphpadmin that there were no passwords for root in mysql, so I added both in the interface, for linux and for localhost.
After that mysql was too broken. I deleted lots of stuff (very hard), rebooted and finally had xampp working again. This time I took heed and only created the first password for linux and it still works.
Thus no password for localhost.
How come this all is happening?
I ran the "lampp security" command and was guided to instate some passwords. After that the simple html page I was viewing required an initial password with lampp as user. Now I don't want my users/visitors (the world) to be barred by a password to my production webserver, so the password requirement for viewing html-files need to be removed. How can I do that?