Not everyone has access to their server logs. The workaround is to call a script which does the logging. In order to call the script, a common trick is to place it in an image tag. The script will get called everytime the page is loaded, unless the browser ignore the images. In order to avoid displaying a broken image icon, the script returns an image to the browser to satisfy its expectations. Some scripts return a small logo; some scripts return a tiny invisible gif in order to avoid adding clutter to the embedding page.