LOS ANGELES -- Californians seeking the names, photos and addresses of sex offenders living in their neighborhoods can now find that information with just a few mouse clicks on a computer.

The state's long-awaited Megan's Law Web site went up on the Internet on Wednesday. State Attorney General Bill Lockyer called it "a remarkable tool for families to protect themselves" from sexual predators.

Opponents say the easy access to detailed information provided by the site -- some of it inaccurate -- will lead to vigilantism while unfairly penalizing rehabilitated offenders.

The site -- meganslaw.ca.gov -- includes information on 63,000 of the state's estimated 110,000 sex offenders who register with local law enforcement, officials said. Home addresses are listed for 33,500 of the most serious offenders.

Detailed street maps on the site display blue dots representing offenders. Visitors clicking on a dot can see the offender's physical description, aliases, type of crime, and in many cases, a photo. Visitors also can search by other methods including individual name.

Lockyer demonstrated the site at a news conference attended by state lawmakers who wrote the bill creating it and Orange County child safety activist Erin Runnion.

Runnion launched a foundation aimed at protecting children after her 5-year-old daughter Samantha was kidnapped, raped and murdered in July 2002. She said that while the Web site would not have saved her daughter -- because the man accused of the crime was not in any database and did not live near her -- it would protect others by putting parents on alert.

"A lot of us as parents are in denial about how common sex crimes against children really are," Runnion said. "Megan's Law being on the Web is going to make it very visual for parents. They can put in their own address and see all those little blue dots surrounding their own home and where their children go to school. That just raises the consciousness, and that's what needs to happen."

Groups opposed to the Internet registry say it will lead to harassment of reformed offenders while failing to protect people from those who plan new sex crimes and don't register.

"Anyone planning to prey on vulnerable victims who is a registered sex offender would not be cooperating with authorities, and their information will not be accurate on the Internet," said Paul Gerowitz, executive director of California Attorneys for Criminal Justice, which lobbied against the site.

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Lockyer acknowledged that about 20 percent of the registry is inaccurate but said he hoped the public would now report flaws and pressure local law enforcement agencies to update their information.

Dozens of other states now have Internet sex offender listings, most of them featuring pictures. The Supreme Court ruled in March 2003 that posting such registries online is not an unconstitutional extra punishment.

In California, Gov. Arnold Schwarzenegger has called for "a more comprehensive measure" expanding the site to be passed by the Legislature. Assemblyman Todd Spitzer, R-Orange, introduced a bill putting information about all California sex offenders online.

Spitzer urged Californians not to harass offenders identified on the site.

"This is not a call to take up arms, this is a call to take up information," he said. "We could lose this tool if the public does not properly utilize it."

Megan's Law is named for 7-year-old Megan Kanka of New Jersey, who was raped and killed by a neighbor in 1994. California established its database of sex offenders two years later.