Website 24/7 Wall St. looked at a number of workplace studies on how people spend time online, and found that most say employees with PCs spend 20-plus hours a week on the Web while at work—and about a quarter of that is for personal use.

Here are the top 10 "time wasters":

1. Social Networks: 1 hr, 14 min/week; apparently, 77% of employees who have access to Facebook from work check it at least once a day.

2. Online Games: 34 min/week

3. Email: 27 min/week

4. Portals like AOL, Yahoo!: 14 min/week

5. Instant Messaging: 13 min/week

6. Fantasy Football – 0.12 hr/week (during season).  According to some reports, fantasy football caused $9 billion in lost productivity in 2009 alone.

7. Pornography – 0.13 hr/week; 29% of workers have looked at pornography while at work.   70% of all pornography traffic occurs between 9am and 5pm.  What is the average amount of time each of these workers spends on adult websites per session? 12 minutes and 38 seconds.

8. Videos/Movies – 0.21 hr/week; more than 161 million people watched an average of 157 videos in August.  The average online viewer watched 9.7 hours during that time.  The average duration of videos was 3.7 minutes.

9. Search – 0.19 hr/week; According to a study by RescueTime, when Google replaced its home page logo with Pac-Man – the playable version of the classic game – earlier this year, it cost the economy a total of 4,819,352 hours of productivity, which researchers estimated was worth over $120 billion in potential productivity.

10. Online Shopping – 0.15 hr/week; In 2009, IT information association ISACA estimated that the average employee would spend 14.4 hours shopping from the office around the holidays.