Google has banned pornography from appearing in its online ads.
The changes went into effect this week.
Notification came in an email to porn site advertisers on Google's Adwords network.
The company said it would no longer allow ads that contain sexual imagery, "including, but not limited to, hardcore pornography and graphic sexual acts..."
Google's Adwords ads appear on millions of sites across the web.
The "promotion of pornography" is still allowed, according to the Adwords policy.
But the ads cannot contain sexually explicit content.
The porn ad ban comes a year after Google decided to remove blogs from its blogger network that contained advertisements for online porn sites.