Never Show an Empty Slot: House Ads as the Floor

A house ad is an advertisement for your own site running in ad space you have not sold: your newsletter, your own product, or a card saying the space is for sale. Every slot should have one behind it, because an empty rectangle earns nothing and tells every visitor, including every advertiser who ever looks at your site, that nobody is buying your space.

The house ad is the least glamorous thing in an ad server and one of the only things in it that costs nothing to run. It is also the only inventory you can fill on a Sunday afternoon with a decision instead of a sale.

What happens when a slot has nothing sold in it?

It falls through. Every position has a floor price, bids below it are discarded, and if nothing clears the floor the slot passes to whatever you put behind it. That fallback code runs in the page rather than inside an iframe, which is why a network tag underneath fills exactly as it normally would.

So the question is never whether to run house ads. It is what sits in which position in that chain, and unlike most decisions in advertising this one can actually be calculated. The mechanism itself is passback, and why the network keeps working underneath is covered in keeping AdSense while selling direct.

What should a house ad promote?

Four things are worth the space, roughly in this order.

• Advertise Here. A card saying the space is for sale, in your most visible position, pointing at a page that says what it costs. One booking from it pays for a year of unsold sidebar. Almost nobody runs this and it has the highest return of anything on the list. See the Advertise Here page.
• Your newsletter. An audience you own outright, with no algorithm sitting between you and it, which later becomes a second product to sell to the same advertisers. It works best directly below an article, where somebody has just finished reading and enjoyed it.
• Your own product or service. Consulting, a course, a book, a membership, a shop. It converts at your own margin rather than at somebody else's commission rate, and you already know what a customer is worth.
• Your best content. The least obvious one. Sending a reader to a second page raises pages per visit, which raises the impression count on every slot you sell. A house ad that keeps people on the site is quietly an inventory decision.

Is a house ad worth more than the network fallback?

Sometimes clearly yes and sometimes clearly not, and the way to tell is arithmetic rather than instinct. Take a sidebar with 40,000 unsold impressions in a month and a network paying $0.60 per thousand for them.

One month, one slot you have not sold, invented but ordinary numbers

Every figure here is invented except the first one, which is exactly right on every site. Put your own click rate and your own subscriber value in.

The bar you are giving up is small, and that is the real insight. Twenty newsletter subscribers a month cost you $24 of network income, or about $1.20 each. If a subscriber is worth anything at all to you across a year, that trade is not close.

The Advertise Here card is the same trade with a longer payoff. It does nothing for weeks, then produces one email from a local business, and that single email is worth more than the slot earns from a network in a year. You are buying lottery tickets with money that was nearly worthless, which is the only situation in which that is a sensible thing to do.

Above the network, or below it?

Once you have those numbers the ordering answers itself. If the house ad is worth more per thousand impressions than the fallback pays you, it goes above the network and takes the unsold inventory first. If it is worth less, it goes below, where it only appears when the network itself has nothing to show, which on most sites is a small share of requests and a perfectly good home for a second or third message.

Most publishers end up with a split rather than a rule. The Advertise Here card runs above the fallback on one or two visible positions, the newsletter card sits below it everywhere else, and the rest of the unsold impressions go straight to the network without ceremony. That is a better answer than the tidy version where every unsold impression is treated the same way, because your slots are not worth the same and neither are your messages.

What makes a house ad actually work?

Mostly that it is treated as an advertisement rather than as a notice. Run down this list before you put one live.

The frequency cap matters more than people expect. A loyal reader who opens a dozen pages a day sees the same newsletter card a dozen times a day, and by the second week they cannot see it at all. Capping a house ad at two or three views per reader per day keeps it working and, more usefully, hands the rest of those impressions back to the paying fallback. That is one frequency cap doing two jobs.

The honest caveat

There is a second version of the same mistake, which is filling every position with your own promotions until the site looks like a parish notice board. An advertiser who lands on a page carrying six house ads does not conclude that the site is busy. They conclude that nobody is buying, which is precisely the impression an empty slot gives, arrived at from the opposite direction. Two house ads on a page is a floor. Six is a signal.

What to do this week

Make one Advertise Here creative at the size of your most visible slot and point it at a page listing what you charge. Make one newsletter creative for below your articles. Cap both, tag both, and leave the network underneath everything else. Then look at the numbers in a month and keep whichever one earned its place.

That is most of the value available here, it takes an afternoon, and the alternative is a rectangle of white space that has been quietly earning nothing since the day you installed the slot.