Yes, site targeting is active in Google AdWords. There’s only two real possible reasons that your ad isn’t active yet: (I’m assuming that the ad and landing page are relevant and fit the guidelines of the ads here. If not…)
1. You’re trying to advertise on a competitor’s site and they’ve listed your domain as not being allowed.
2. You didn’t bid high enough to show up on the target site, so you won’t until your competing bidders’ ads are done.
Either way, you should email the AdWords Support to find out for sure.
I hope this helps. Create a great weekend.