Getting the right setup
The AdWords API can be used to manage both keyword and website criteria within the same ad group. However, you do need to make sure your ad groups are properly configured before they'll accept both those criteria types. In order for your ad group to accept keyword criteria, it must have its keywordMaxCpc and/or keywordContentMaxCpc attributes set to your maximum CPC bid. In order for your ad group to accept website criteria, the siteMaxCpc attribute needs to be set as well. Failing to have a value set for siteMaxCpc is a common cause of SOAP errors of type 74 while trying to add website criteria to an existing ad group. In fact, a misleading message may appear: "This criterion type is invalid. Acceptable values are 'Website' and 'Keyword'. Websites and keywords may not be used in ad groups in the same campaign." Rest assured, the spelling of "Website" did not change overnight. You may just need to set your siteMaxCpc value.
Which bid gets triggered?
Although controlling both keywords and websites within the same ad group adds a new range of possibilities for campaign structure, it can be confusing as to which bid will be triggered under different situations. This information is available in this article in the AdWords Help Center but it helps to visualize a few common scenarios.
For the following examples, let's suppose that we have added the keywords "Mars" and "rover" as well as the website "nasa.org" to our ad group. In our campaign we have set the bidding strategy to CPC and have enabled our ads to appear on Google search, Search partners, and Relevant pages across the entire network.
- A user searches for the phrase "Mars rover" within Google or on one of Google's search partners. AdWords will always use the keywordMaxCpc bid to determine if your ad should be placed.
- A user visits NASA's new Mars rover website with nasa.org as the domain. In this case, because you have nasa.org as one of your Website criteria, the bid will be either be the siteMaxCpc value from the ad group or the maxCpc from the Website criteria. If there's a maxCpc value defined in the criteria, then it will take precedence. Even if this website would trigger the keywords in your ad group, the placement-related bidding values will always take precedence as they're considered more specific.
- A user visits the Mars rover's manufacturer's website, which happens to be on the content network (i.e. it is an AdSense enabled website). The keyword criteria "Mars rover" is what ends up triggering the ad. In this case, AdWords will first check the maxCpc value set for the keyword that triggered the ad, if this is not set, the keywordContentMaxCpc value from the ad group will be used. If keywordContentMaxCpc is not set, it will use the keywordMaxCpc value. It will not under any circumstance use the siteMaxCpc value.
(By the way, if you're curious about which bid will get used if an ad is triggered by both a keyword and a website in the same ad group, it will always be the bid associated with your website.)
If you've set up your campaign for CPM bidding (because you'll be running image or video ads on the Content network, and not text ads on the Search network), then the only relevant ad group bid setting to configure is siteMaxCpm. This simplifies setup considerably compared to the options available when you're using CPC bidding.
You can add both keyword and website criteria to the same ad group, and the siteMaxCpm bid will always be used when determining what you're willing to bid for each impression your ad receives.
Both keywords and website criteria will be able to trigger your ad in the Content network, with the caveat that your keyword criteria won't generate any impression or click-related statistics when used to trigger ads in the Content network.
--Adam Rogal and Jeffrey Posnick, AdWords API Team