This is a map I did back in 2010, reflecting seven days of my internet activity. More precisely it is the activity of my internet browser. A plug-in was tracking different parameters. Those were the uptime of the browser, the browser usage (time the browser windows was actually in focus), time spent on each individual page (the circles), the time of day and the weekday of each visit, the total tabs that were created during the week and the average number of tabs open at the same time.
The legend can be read from right to left alongside the time of day to which it is in absolute relation (0–24 h). That means a one hour long line reflects one tab.