March 20-23 AMA with Jan van der Crabben, CEO of Ancient History Encyclopedia


Ask your header bidding, ad quality and viewability questions the week of March 20-23 to Jan van der Crabben, CEO of Ancient History Encyclopedia. Jan will be answering your questions throughout this time.

“We’ve abandoned the waterfall completely and we’re doing 100% header bidding with great success. OnScroll, Sovrn’s in-view ads, work really well for us (see this case study). You can also ask me questions about switching over to SSL, how to secure your site against hackers and how to speed up your site.” - Jan van der Crabben

About Jan:
I am the Founder and CEO of Ancient History Encyclopedia, a non-profit company whose mission is to improve history education worldwide by creating the most complete, freely accessible and reliable history resource in the world. I’m neither a professional coder nor a pure businessperson, but through my varied background I have managed to combine both technology, business, and a love of history to create the world’s most-read history encyclopedia.

Much of my time is spent improving and optimizing our advertising revenue. Like most publishers, we started with AdSense and then transitioned into a waterfall setup… my worst nightmare! Waterfalls require constant maintenance and guesswork, which makes them rather unpredictable in the long term. It’s also easy to lose out on revenue when trying out a new ad network. Then came header bidding, which is the solution! There’s still tweaking involved, but far less and there’s no chance of losing revenue by adding a new network.

I also work a lot with SEO, online marketing, and I designed our website’s subscription service: Advertising revenue is very seasonal, so we added a subscription service to buffer the seasonality with a constant revenue stream. It’s not making as much as ads, but it does provide a good buffer during the summer months, where ads are down.

Something interesting about me:

I founded my first web company when I was 16, studied journalism at university, followed by a successful career of over ten years in game design, only to return to starting a business.

Where to connect:

Reminder! If you want to post questions, then you need to Sign Up for Sovrn Community.

Note: This is the actual AMA thread! Please place your questions in the thread below for Jan.


Hello everyone! It’s a pleasure to be featured in this AMA and I am looking forward to answering your questions. I’m very excited about the revenue potential of header bidding as well as alternative techniques, such as Sovrn’s OnScroll. I’ll do my very best to answer any question, but please keep in mind that I’m coming from the publisher’s perspective and I do not work for Sovrn.

Let the AMA begin! :smiley:


Hello Jan!
If you’re using an ad server, does including in-view or viewability type ads in your website’s ad inventory negatively affect direct, guaranteed, or other inventory?



Thanks so much for doing this AMA. We appreciate the input and wealth of knowledge you have provided since joining our community!

I read your case study regarding implementing Sovrn’s Viewer Engaged Takeover Onscroll product and found it very encouraging that you saw a 26% boost in revenue. Would you recommend this product to other publishers?

Follow up: We are always interested in feedback, so, are there any drawbacks that you have seen with the product that should be addressed?



@jrosario & @jhgerlach Thanks for your comments! Since both of your questions are going in the same direction, let me answer them together.

We haven’t seen any negative impact on our other inventory when using viewability ads (OnScroll / VET) on our website. Some ad network partners’ legal wording restricted us from refreshing their ad units, but after some negotiation we agreed that it was fine. In terms of directly sold revenue, we haven’t got much of that… we haven’t got a sales team, after all. We did have a few direct sales, but we don’t guarantee any inventory anymore: We only offer them a fixed-CPM bid to compete with our header bidding. From our perspective, most advertisers that we’ve encountered aren’t willing to pay a high enough CPM rate to warrant guaranteeing inventory. If you’re a bigger website, like the New York Times, I’m sure that direct sales are absolutely worth guaranteeing, but they’re not for us.

In terms of drawback, we only had one initial implementation problem (we run two sites and the implementation got mixed up), which we solved in the end by implementing OnScroll / VET directly in the website code, not through DFP. No big deal!

I just learned today that we can even put passback tags into OnScroll ad units. Perfect! The problem with AdSense as passback is that you’re not allowed to refresh their ad units, and you’re not allowed to place them into a scrolling box… so that sort of eliminates OnScroll. However, we will use some affiliate ads suitable for our site (Amazon, Bookdepository, Grammarly) as passback for when there’s no OnScroll demand.

In summary, I’d absolutely recommend VET / OnScroll to other publishers.


You mentioned securing your site against hackers - what’s the best way to do this?


Jan, thanks for asking questions. I took a look at your site and was enjoying a great page on “Tlahuizcalpantecuhtli” and noticed how long the page is and how many ads you have on the right rail. Can you talk about how you maintain a decent viewability percentage for your ad units on that right rail for such a long page?


Thanks for bringing up security. Our website was hacked in early 2014, and rather insidious links to illicit websites were inserted very sneakily: They only showed up for Googlebot, but not for normal visitors. We tracked down the attack to a vulnerability in Wordpress of a blog which we were hosting on the same server as our main site (which is custom-built).

For security, one cannot state this often enough: Always upgrade your content management system and all of its plugins! Whenever you see an upgrade… hit the upgrade button. This is especially true for Wordpress, as it’s ubiquitous and therefore a very popular target for hackers. There are several security plugins for Wordpress, too. Automattic’s own Jetpack already comes with a few basic features. I can also recommend a few blog posts from Tsohost (the hosting provider that’s sponsoring us):

Lastly, what we did after the hack was to put a web firewall (WAF) and content delivery network (CDN) in front of our site. That not only gives you amazing security for a surprisingly low price but it also speeds up your website very significantly.

Many people use Cloudflare (which has a free plan with very basic security), but I would highly recommend Sucuri. Their content delivery network is fantastic at speeding up your site and their web firewall is much better than Cloudflare’s. I would also tell you to stay away from Sitelock, as we’ve had bad experiences with them.

Even if you don’t want to pay for a web firewall, at the very least get a content delivery network in front. To me, Cloudflare is the bare-minimum must-have for any website, if only for the speed boost.


Thank you for your kind words on the unpronounceable Aztec god! Viewability always comes with a trade-off I feel. To maximize viewability, you have several choices:

1) You place more ad units above the fold

There’s a limit to how much you can do that, as it not only creates bad user experience but may also earn you an SEO penalty by Google. For us as a non-profit, user experience is super important, so we have opted to only place a single 300x600 ad unit (which also receives bids for 300x250 and 160x600) above the fold.

2) You load ad units dynamically as the user scrolls

That’s quite a bit of development work where, especially when combined with header bidding, so we opted not to go down this route. Also, you’re losing out on bids that you might receive for less-viewable inventory.

When we switched to header bidding, we were surprised to see how even our 728x90 ad unit at the very bottom of the page was receiving good CPMs. In the waterfall, we got maybe $0.20 CPM out of this unit, and now we’re getting something like $0.80 CPM. Probably only about 10% of our users view that ad unit: In order for dynamic loading to be worth it, we’d need to average out at $8.00 CPM for viewable-only impressions… unlikely!

3) You use Onscroll

Luckily, Sovrn has a technology that allows us to combine the two: OnScroll. We have got our standard header bidding ad units on the page, always loaded. We get the CPMs for those. Whenever a user scrolls down to such an ad unit, and views it for 30 seconds or so, OnScroll comes in and reloads the ad unit with an OnScroll ad (if it has demand for that impression). The CPMs there are good and the fill rates are decent.

We’re also going to try adding a fifth ad unit which is purely OnScroll (and sticky to the browser window) on the side of our super long articles (only inserted for articles of 2,500 words or more). Let’s see how that will perform.

General thoughts

Lastly, I also feel that viewability is often overrated. Back in our waterfall days some of our networks kept pushing us for higher viewability. So we ran several experiments, moving ad units around and changing which ad network was above the fold or below the fold. We saw only very minimal average CPM differences. That was over a year ago, so maybe this has changed now, I’m not sure.

@RobBeeler, as you’re from AdMonsters, I’d love to hear your opinion on this, too.

Disclaimer: Sovrn didn’t ask me to say any of this, it’s my honest opinion, even though it sounds like an ad for Sovrn. :wink:


Any last questions before the end of the week? :smiley: