Pew Research, in November 2011

Pew Research, in November 2011, polled a random sample of 799 U.S. teens about Internet use. 49% of those teens reported that they had misrepresented their age online to gain access to websites and online services.
Find the margin of error for this poll if we want 95% confidence in our estimate of the percent of American teens who have misrepresented their age online.