Hits are requests for files from a server. When you visit a web page, your browser has to request all the files that make up that page to be delivered to you. Hits do not measure how many times the site was visited, nor how many visitors the site has. They don’t even measure how many individual pages were loaded. They only measure how many times the server received requests for files. If your site’s home page has 100 images, and a single person visits that page one, you just got 100 hits. Congratulations.

Don’t measure your site’s traffic in hits, then. Because it’s meaningless.

When you skin (or add “wallpaper”) to a website, you typically fill the remnant space on either side of the page content with your branding creative. As well, the wallpaper may show in the “whitespace” within the content. Skinning allows all of the content of a site to remain unobstructed, while allowing for interesting, attention-grabbing branding executions. Skinning can make the site appear as if it’s being directly sponsored by the advertised brand.

Of course, a bad skin (too busy, too ugly, too intrusive) can have a negative effect on a visitor’s experience. While skinning is better than using a voken, it must still be handled carefully to create a good experience for the visitor, the advertiser, and the publisher.

A voken, or “virtual token” is a Top-Layer Animation advertisement that appears and covers over content on a website. Not necessarily user-initiated, these ads, while able to seize the visitor’s attention, can be quite annoying. Advertisers and clients have raved about their effectiveness on a click-through basis, but that’s likely because they were tracking the “Close” button as a click, and thinking that accidental clicks on the ad count as being effective.

Skinning a website can have similar attention-grabbing effect without being near as annoying.

% Comp UV: (Or, Percent Composition of Unique Visitors) The percentage of a site’s visitors that are in your target demo.

This is why reach ain’t everything. If you have a small demo especially, you might not want to blow a ton of money on big sites with huge reach to hit them. If you try to figure out smaller sites whose visitors are highly-composed of your demo, you can probably buy on a bunch of those sites for cheaper, and still end up getting the same (or close to it) reach.

Reach: The percentage of your target demo that visit the website you’re advertising on.

If you’re looking to hit as many people in your demo as possible by buying on as few sites as possible, reach is your metric of choice. If your target is pretty broad, you’re going to be looking at buying on the big sites like Yahoo! or even Facebook.

But reach ain’t everything.

If you have a very narrow target, you can still hit them usually by going on the big sites (my Yahoo! reps tell me that when you combine all their properties together they approach 100% reach), but it’ll cost you a decent chunk of change. Why not find a bunch of smaller sites that your demo visit, and buy on them for cheaper? That’s where % Comp UV comes in.