My Website: is throwing an error that I have been unable to resolve

I’m not sure what was added/removed but now I get an: Notice: is_main_query was called incorrectly. In pre_get_posts, use the WP_Query->is_main_query() method, not the is_main_query() function. See Please see Debugging in WordPress for more information. (This message was added in version 3.7.0.) in /home3/lrevell8/ on line 4147