[support] Drupal 7/Zen Theme Question

[Hakan]

In Drupal 7, I have created a subtheme from Zen which I am - whenever I
have some spare time - slowly developing into the custom theme for one
of my websites. Obviously this is a learning experience although I do
have a little experience from Drupal 6 several years back.

I have installed Firebug under Firefox and am using it to look at
various properties of one of the pages I am theming. My footer message
shows an id of "block-block-1" - which I have then used to assign the
appropriate CSS property values. I would, however, like to understand
where/how that id is generated and did a grep of the entire website
looking for that particular id. I only found it in the Zen theme and in
my derived subtheme, not in any particular Drupal file.

Could someone who knows Drupal 7 better tell me where that particular
id is generated for the footer message?

Thanks.