If I remember correctly, those bars are usually a different colour from the rest of the page (probably a shade of blue or green). Yours looks just like a footer because it matches the colour of your page header (black).

Correct, it looks like footer. So, you did not notice it in first glance?

I noticed it only when I scrolled. And then I was disappointed there was no hide button :-D

I didn't even notice the bar the first time I read the article, I actually had to go back to the site to see what you were talking about in this comment.

Oh, I see. That's too bad that not many people are noticing it. Any ideas how I can improve it without making it look too spammy or intrusive?

You could animate it to slide up a few seconds after page load.