At Admin Panel -> Settings -> Switches, the "alexa graphs" switch enables a graph of website visitor activity from alexa.com. For example, http://traffic.alexa.com/graph?&w=400&h=220&u=webmastersite.net is one of the graphs. The graph is resized to be wide and short and placed near the other website information on the listing details page. This can be useful in a similar way to the pagerank option, but is more detailed and less intuitively easy to read than pagerank in how it tells people the popularity of a site. Turn it on if your visitors want every detail, or off if they don't want to be distracted with unnecessary stuff.