PHILADELPHIA - About 1 percent of Web sites indexed by Google and Microsoft are sexually explicit, according to a U.S. government-commissioned study.

Government lawyers introduced the study in court this month as the Justice Department seeks to revive the 1998 Child Online Protection Act, which required commercial Web sites to collect a credit card number or other proof of age before allowing Internet users to view material deemed “harmful to minors.”

The U.S. Supreme Court blocked the law in 2004, ruling it also would cramp the free speech rights of adults to see and buy what they want on the Internet. The court said technology such as filtering software may work better than such laws.

The American Civil Liberties Union, which challenged the law on behalf of a broad range of Web publishers, said the study supports its argument that filters work well.

The study concludes that the strictest filter tested, AOL’s Mature Teen, blocked 91 percent of the sexually explicit Web sites in indexes maintained by Google Inc. and Microsoft Corp.’s MSN.

Wow, I’ve seen almost an entire 1% of the internet!

(side note: AOL gets props for flitering technology… Jason Calacanis will be blogging about this soon, I bet!)