i’d rechecked your web-code… you did a workaround with display: none..
it works but is not clear coding.
you can look to the footer.php in your theme-folder (its under your-web-root/wp-content/themes/<and here the theme name>), and if it’s not using partials you can delete:
the following lines:
<div id=”theme-attribution”>
A
SiteOrigin
Theme
</div>
but first inform yourself about child-themes (google helps you ?? .. you can make a child-theme and edit your footer.php there.. so you have no problems, if your theme got an update…
good luck
