You do that with CSS by adding something like this to your Child Theme’s style.css: .designer-info {display:none;}
To find that, I used the “Inspect Element” feature of Firefox by right-clicking over the text and then doing a bit of looking at the code.
the ‘powered by’ text is set from within /inc/extras.php of your theme;
in this section:
<div class="designer-info">
<?php
printf( '<a href="%1$s">%2$s</a> <span class="sep">%3$s</span> %6$s <a href="%4$s">%5$s</a>',
'http://themecot.com/wordpress-theme/keratin/', 'Keratin Theme', __( '·', 'keratin' ), 'http://wordpress.org/', 'WordPress', __( 'Powered by', 'keratin' )
);
?>
</div>
if you want to remove the text directly by editing the files (ideally from within a child theme), please post in https://wordpress.org/support/theme/keratin/ get theme specific suggestions.
[closed as duplicate of https://wordpress.org/support/topic/removing-powered-by-wordpress-from-keratin-theme?replies=4 – please continue with the original topic]
