It appeared on all blog-post pages only. This is featured posts page: http://goo.gl/fYC7uu
I asked hosting provider to stop this warning from appearing on post pages by disabling php module, I'm not very good at it.
Error log is : Error with Blog tool plugin. Warning: Invalid argument supplied for foreach() in /qa-base.php(572) : eval()'d code 189
there're hundreds of this same statement.
I use many plugins, by this time all of them worked in peace with each other. :)
I use CKEditor, Markdown, Tag description, Comment Voting, Embed, Extra QF? Hashtagger, Most active users, on-s-notification, tagging-tool, social sharing and so on.