for cookie enabled browsers

As they state here, You can optout to prevent your computer from having the X10 "pop-under" ads appear But only for 30 days at a time.
Opting out will place a cookie on your computer that will disallow X10 pop-under ads from appearing, and remember when clearing out your cookies not to remove x10's cookie

Optout Now

At the bottom of this forum... A (your) choice to optout of x10 popunder ads.

Wheather these optout cookies work or not, I wouldn't know and will never know, If you choose to optout please let me know if it does as it states

I allowed myself to be scummed by ads.x10.com to check out the optout cookie and relized with a little addition to the url, (say 10 years or 3652 days) I can optout for 10 years (My expiry date: 26/02/12).

Just right click on the "Optout Now" link above and select "copy shortcut", past it in the address bar and change the "DAY" from 30 to 3652

And for the optout cookie to work, you have to remove *.x10.com from your "Restricted sites" and enable cookies for x10.com