I downloaded the Zen theme and FTP'ed it to sites/all/themes.
It appeared in my list of themes, and I clicked on the Default setting. I got this error:
Fatal error: Call to undefined function render() in /home2/wvwworg/public_html/scholaclasses/forum/sites/all/themes/zen/templates/block.tpl.php on line 12
and now I can't get back to my Administration Themes page to change it back to Garland.
I was hoping it would be a simple matter to change the theme to a mobile-friendly theme, but apparently I got in over my head very quickly.
Can anyone help?