Porn sites opening on iPhone and iPad

Clear Safari history, cookies, and data.

Tap Settings, then Safari.

• Tap Clear History and confirm.
• Tap Clear Cookies and Data and confirm.

Note: If you have saved passwords and other data with websites, this info will be deleted, and all open webpages will be closed.

Try doing a factory restore of you're router.

Is your phone jailbroken?

You need to do this...

Settings -> Safari -> Advanced -> Website Data -> Remove All Website Data

This is differernt than the "Clear Cookies and Data" option you tried and that's listed above.

What kind of sites are you visiting before these popups begin?

I saw it yesterday while viewing cnn.com

deleteing the website data fixed it for me.

If the above don't help, may want to remove infected adware, as per Thomas Reed's tips: http://www.thesafemac.com/arg/

If this is happening while connected to a home router, your router may be hacked.