DoubleClick Ads: Possible issues with googletag.definedSlots not matching googletag.display on a page

Question

I have a large publication site that has to be upgraded with the new DoubleClick ad system.

There are two tiers to this. The first is defining the slots in the head, and the second it to add the markup into the page body. Example: http://support.google.com/dfp_premium/bin/answer.py?hl=en&answer=1638622&topic=28788&ctx=topic

Now, would it be an issue if you defined a whole lot of slots, but only to show a subset of the defined slots on the page?

In short. Not all the slots are being used on the page. Esp. inner pages where there isn't as much ad real estate as on the homepage.

Answer 1

It will be an issue if you are using SRA (Single Request Architecture) to make ad calls for your webpage.

For people who don't know what SRA is, it's a feature where ad call for all the ad slots on the page is made in just one single ad call. Advantages are

• Guaranteed Roadblocking
• Reduced latency

With SRA enabled, a single ad call for all the ad slots on the page is made when a first matching googletag.display for the google.defineslot is found in the source code of the body.

For example, you've 10 google.defineslot in the header, and 1 googletag.display in the body, ad call for all the 10 ad slots on the page is made when first matching googletag.display for the google.defineslot is found in the source code of the body. DFP will serve a creative if available and record an impression, for all the 9 ad calls that aren't defined in the body, DFP will record an unfilled impression.

The best feature in DFP is Forecasting and Forecasting in DFP is based on the ad calls received by DFP. If you are forecasting for a particular ad unit and for a particular size, which is not actually being used to display creatives on the webpage, but defined on the webpage with SRA, your forecast results show huge impressions available, and if you book a campaign based on those results, it may under deliver and worst case scenario - may not deliver at all.

You should actually implement the googletag.define slot in the header and googltag.display not in the body with SRA only when you are actually planning to implement the slot in the webpage and you are planning to forecast the available impressions in order to avoid over booking of the campaign. And the actual advantage is you'll not see a blank ad space on the webpage with this implementation.

In case if you aren't using SRA, ad call for each googletag.defineslot is made only when matching googletag.display is found in the body.

For example, you've 10 googletag.defineslot in the header and only 6 googletag.diplay are defined in the body, only ad calls for the matching 6 googletag.defineslot are made by the webpage.

If you want to forecast with this method, you'll have to implement googletag.defineslot and googletag.display in the header and body - issue is that you'll see a blank ad space on the webpage. In order to avoid this blank ad space issue you'll have to traffic House ads.

Answer 2

That wont be an issue at all... I did the same thing with no problems but to tidy up my page I made a jQuery plugin that only defines and and displays the ad slots it actually finds/needs on each page... check it out if you are interested.