Image tracking not working


I’ve just installed Piwik and now I am testing it.
I also tried to implement the image tracking. I put the code into my html file, but I cannot see any hits in dashboard. The statistics with JS is worling OK.
When I try to show the tracking image with a provided link, the image shows, but in my dashboard I cannot see any hits. Is it possible that the showed image are tracked somewhere else than in dashboard.
Does it matter where you include the code into html file?