No, the percentages do not have a sum of 100%.
Work Step by Step
Let us round each of the percentages down--to the closest 10%. Google: 40% Facebook: 20% Yahoo!: 20% YouTube: 20% Windows Live: 10% Wikipedia: 10% $40+20+20+20+10+10=120$ People are not limited to one website per day--they can visit as many websites as they wish. People marked (on the survey) that they visited multiple websites on a day.