Show message at every page regardless page content I need to show some message for user for every page at my site.

I've tried Rules action "Content is viewed" and I see message, but only when some node is displayed.
I don't see message when I open User page, or page with Taxonomy term, or some View page without nodes as content.

How can I show message at every page of my site regardless page content?
(Rules or Hooks or ...?)
Why not to write it directly in the template? Or create a Block which you show in the header? or do you need to use the drupal_set_message() Message?

You can use "Drupal is initializing" event at Rules.