Error undefined variable

Hello,
I have a problem with the 2.5 version of the template.
I got an error in articles pages. Could you help me on that ?

Notice: Undefined variable: gkContent in /homez.94/snacklep/www/templates/gk_coffe/layouts/blocks/main.php on line 42
style=width:>
Notice: Undefined variable: gkComponentWrap in /homez.94/snacklep/www/templates/gk_coffe/layouts/blocks/main.php on line 62
style=width:>

screen.jpg

Please go to template settings, open 'developer settings' tab and choose option to generate columns width in header section not in style tags. For future, displaying errors option should be disabled in your PHP configuration - this is required by Joomla installer.

Ok it worked perfectly
Many thanks
Bastien