LESS could not create a directory in public://less/51761ea74e5068.61766466/sites/all/themes/theme_name/css
Warning: Invalid argument supplied for foreach() in drupal_pre_render_styles() (line 3311 of /home/seat3/public_html/site_folder/drupal/includes/common.inc).
Warning: Invalid argument supplied for foreach() in element_children() (line 6300 of /home/seat3/public_html/
To solve this issue need to give 777 permissions "/var/www/site_folder/htdocs/sites/default" at least need to gave 775.
Your drupal site
files directory has to be writable by your webserver.
Below specified "Ubuntu command" for change permissions.
/var/www/site_folder/htdocs/sites$ sudo chmod -R 777 default/