Hi, Gantry doesn't support widget accessibility, so there is nothing else you can do other than hide the warnings, it's definitely not affecting your site in any way.
Generally, you'll want to always hide warnings and notices on live sites for security reasons. The only messages that are important are fatal errors, which even if errors are hidden, result in a blank white screen which is a dead giveaway that you need to turn debug on to see what it is.
I go into a lot more detail on this subject in our FAQ:
www.rockettheme.com/forum/index.php?f=29..._v=viewtopic#p847421
Here is an excerpt from that post that shows how to modify your php.ini to hide warnings and notices, but still show errors:If you are seeing these messages, it does not indicate an issue with your website, and these messages can be safely ignored. However, they do not look very good all over your website. To hide the messages, you'll want to set your php.ini file to hide warnings and notices.
This setting is made in your hosting accounts php.ini file. If you're not sure how to do this, contact your hosting company for assistance.
; - Show all errors, except for notices and coding standards warnings
error_reporting = E_ALL & ~E_NOTICE